I'm pretty confident you're not ISFP. You seem clearly intuitive to me. In fact I would type you as Ni primary.
That's largely an intuitive read, but I'll point to a few clues. These are gross generalizations, but 1 clue is that ISFPs are, of all types, typically the least interested in profiling. You seem very interested. Another clue is that your two best friends are intuitives. The one dichotomy that's most correlated to compatibility is S/N. Your primary goal of helping people is not at all exclusive of ISFP, but is especially aligned with the NF temperament.
Your comment at the beginning about how you imagine what other people are feeling/seeing sounds Ni/Fe to me. You seem pretty clearly Fe to me, and not Fi. An Fi primary will tend to go inside and reflect more on their own feelings. You seem to be much more in tune with what other people are feeling, which reflects in how you talk about them. When you go into your 'mind palace' I don't think you're going into Fi. I think you're going into Ni.
INFJs and all types with Fe as a primary or secondary function, are typically very sensitive to indifference. The way that you described how your INTJ brother won't respond and how that makes you feel like you may have done something wrong and then you keep talking to try and get an opinion out of him is very Fe.
INFJs are often mistyped as perceivers since we lead with a perceiving function. We often tend to have messy rooms and like to follow our inner bliss. The J/P difference is much more apparent in extraverts. All introvert types are commonly mistyped at the J/P difference.
You're ultimately going to be the best qualified to type yourself, provided you have accurate information about the types, so If what I'm saying doesn't fit for you then trust your gut. That being said, this is a decent INFJ profile:
http://www.personalitypage.com/INFJ.html
Some things I might tweak, but it's one of the better ones I've found online. How much does that resonate for you? Anything in particular that you don't relate to?
I've heard ENFJ, ISFP, ENFP, and INFP before for my types, but never INFJ, so this is an interesting difference. XD I read through it and can relate to several large chunks of it and see them in myself very strongly but don't really get a feeling that "Oh, this is my type!" But I do tend to do what it mentions in there somewhere about 'becoming so set in thinking they're right that they block out other opinions' or however it was worded, so, I'm trying very hard to keep an open mind and be open to other possibilities than just IxFP. XD
I'm just going to go through and do a breakdown of what I do and don't relate to, maybe you guys have more input on why I relate to some things and not others that can enlighten me further.
"constantly define and re-define the priorities in their lives." I do tend to do this, especially with career choices. I go back and forth CONSTANTLY from choosing a future career in dance, a future career in art, and a future career in psychology. And every single time I say 'I definitely know this is right!' but the next day... xD (I do this with my type, too, I think I mentioned that somewhere in my video, I go 'OMG THIS IS TOTALLY RIGHT AND I'M NOT GOING TO CHANGE IT!' and then... less than a week later... xD)
"They know things intuitively, without being able to pinpoint why, and without detailed knowledge of the subject at hand. They are usually right, and they usually know it. Consequently, INFJs put a tremendous amount of faith into their instincts and intuitions. This is something of a conflict between the inner and outer worlds, and may result in the INFJ not being as organized as other Judging types tend to be. Or we may see some signs of disarray in an otherwise orderly tendency, such as a consistently messy desk." I have this natural instinct for if my friends are hurting and I always know the exact right time to bring something up. I also have random people I see in a crowd where I immediately become drawn and attracted to them, such as 'I can tell this person is a very kind person and I want to get to know them and become their best friend for all of life!' That also goes the reverse way--I can look at someone and go 'I feel uncomfortable around this person. There must be a reason for that.' and then I start avoiding being alone with them. So far, my instinct has proved right on people every time but once. And my room is always trashed. I'm actually a really messy person. XD
"INFJs have uncanny insight into people and situations. They get "feelings" about things and intuitively understand them. As an extreme example, some INFJs report experiences of a psychic nature, such as getting strong feelings about there being a problem with a loved one, and discovering later that they were in a car accident. This is the sort of thing that other types may scorn and scoff at, and the INFJ themself does not really understand their intuition at a level which can be verbalized." I mentioned earlier my 'feelings' about what kind of people people are. I haven't really done the whole 'psychically know someone I love is hurt!' thing before, but one time I was at a dance competition and my INFJ best friend who I mentioned in the video was in a dance class very far away. My mom got a phone call as I was warming up and I had a weird feeling about the phone call but I didn't think too much of it. Then my mom walked over and told me my INFJ best friend had dislocated her knee. I started getting really agitated, really stressed out, really snappy, I didn't have my head in the game onstage and completely freaked out and messed everything up, and I was walking offstage I got a really sharp pain in my knee, which I later found out was around the time that the doctor relocated her knee. Does that count? XD
"Consequently, most INFJs are protective of their inner selves, sharing only what they choose to share when they choose to share it. They are deep, complex individuals, who are quite private and typically difficult to understand. INFJs hold back part of themselves, and can be secretive." Nobody ever really understands what I try to verbalize except for my INTP boyfriend, and he's the only person who really truly knows everything that goes on in my head. My INFJ and ENFJ friends know me very well, too, but not quite as well. Sometimes I feel not understood by them, but more understood by them than the majority of the people I know.
"But the INFJ is as genuinely warm as they are complex. INFJs hold a special place in the heart of people who they are close to, who are able to see their special gifts and depth of caring. INFJs are concerned for people's feelings, and try to be gentle to avoid hurting anyone." I'm not even going to go into detail on this one, just know that this is exactly me.
"They are very sensitive to conflict, and cannot tolerate it very well. Situations which are charged with conflict may drive the normally peaceful INFJ into a state of agitation or charged anger. They may tend to internalize conflict into their bodies, and experience health problems when under a lot of stress." Anything even slightly stressful just drives me over the edge and I freak out at everyone for everything. (I have literally gone to my room to cry because my mom corrected me while I was making cookies before.) Then I immediately feel bad about making everyone else feel bad or freaking out on someone and get angry at myself, then the whole thing loops. I'm a really busy person and I almost constantly have tense, tight, sore shoulders, stabbing stomachaches and painful headaches.
"Because the INFJ has such strong intuitive capabilities, they trust their own instincts above all else. This may result in an INFJ stubborness and tendency to ignore other people's opinions. They believe that they're right." Mentioned this earlier.
"On the other hand, INFJ is a perfectionist who doubts that they are living up to their full potential. INFJs are rarely at complete peace with themselves - there's always something else they should be doing to improve themselves and the world around them. They believe in constant growth, and don't often take time to revel in their accomplishments. They have strong value systems, and need to live their lives in accordance with what they feel is right. In deference to the Feeling aspect of their personalities, INFJs are in some ways gentle and easy going. Conversely, they have very high expectations of themselves, and frequently of their families. They don't believe in compromising their ideals." <--Me.
"INFJ is a natural nurturer; patient, devoted and protective. They make loving parents and usually have strong bonds with their offspring. They have high expectations of their children, and push them to be the best that they can be. This can sometimes manifest itself in the INFJ being hard-nosed and stubborn. But generally, children of an INFJ get devoted and sincere parental guidance, combined with deep caring." I'll have high expectations with my children when I have them (which won't be for a long long time) but I don't think I'll push them. I tend to see myself as the parent that ends up as more of a gentle friend than an authority figure. (Good thing my INTP boyfriend sees himself as the really strict parent x'DD)
"In the workplace, the INFJ usually shows up in areas where they can be creative and somewhat independent. They have a natural affinity for art" Yes, but I fail at science and math. So hard. "INFJs can also be found in service-oriented professions. They are not good at dealing with minutia or very detailed tasks. The INFJ will either avoid such things, or else go to the other extreme and become enveloped in the details to the extent that they can no longer see the big picture. An INFJ who has gone the route of becoming meticulous about details may be highly critical of other individuals who are not." Basically.
See, the thing that throws me for a loop about the INFJ type and me is
I definitely use Te as an inferior function. Thinking is my least used function, I can tell you this right now, and I fit every single description of Te and don't even relate to Ti in the slightest. This is the one function I am 100% sure on. Te is my inferior function.
I know that I use Se as an INFJ does, but I think it's pretty high up in my stack. I could only be using it as a tert function, but I'm pretty sure it's my aux function. (That may be my ISFP bias coming into play, though, but I do use Se a lot.)
And I honestly, really, truly thought I used Fi. (And I know my F is probably either my aux or my dom function, because I use a freaking lot of it.) Can someone try to explain to me the difference between Fe and Fi? Simply? XD *gets lost in really long and complicated descriptions of things*
I'm not closing INFJ out as an option but those are the things that throw me for a loop with this, so if someone could help me figure all that out that'd be nice
Also, it's really hard for me to
word things. Because my thought process consists almost entirely of tiny bits and pieces of sentences, singular words, pictures, emotions, and feelings about things and people. You can't talk to someone with half-sentences, singular words, you can't show them pictures, and you can't tell them exactly what you're feeling. So it's really hard for me to describe myself, my thoughts, or my feelings to people, especially on MBTI and everything, because I don't use a whole lot of words in my thinking process, but you kind of have to use words if you're gonna talk. XD Even now I feel like I haven't described myself very well at all.
(In case this has any correlation to what type I actually am: The types I relate to the most description wise are ISFP, INFP, INFJ, ESFP, and ENFJ (but only a little bit on the ESFP and ENFJ). I'm pretty sure I'm one of the three I types I listed because I know I'm an introvert, though.)
Also, my reason for being so interested in MBTI, as a side note for what you said on how ISFPs are usually not very interested in MBTI, is that I don't really understand myself. I know me, but I don't know why I am me. Why do I think this way, why do I do this, why do I act this way, why do I react this way etc. I feel like MBTI is sort of a journey of self discovery and all, you know? Plus, I tend not to TELL people how I'm thinking, or feeling. I SHOW them. "This song really describes how I'm feeling right now", "This video of this character from a TV show is something I REALLY relate to". My ESTJ mom, as I've mentioned before as well, doesn't understand me at all, so I'll show her the pieces from several different MBTI profiles that really resonate in me and say "This is me!" So I guess it's a way of getting to know myself and also showing other people who I am, if that makes any sense at all.