Well, it is a bit difficult to weigh things out for you, without having any real information to go on or observation of you...
Although there are similarities between INFJ and INFP, the motivations are different (similar to INTJ and INTP "almost being the same" but not really). They are both NFs, but operate off different functions.
INFJ runs off Ni but expresses Fe. Thus, what you see on the surface tends to be more structured, more desire on closure, a more formalized sense of interaction with others (because they use Fe rules to express commitments). They tend to speak with more detail or at least with more of a sense of delineation in what they say. And internally, because of Ni, INFJs are very able to see other viewpoints as "equal" if different. They will judge people more often based on their actions or what they express.
INFP runs off Fi but expresses Ne. They tend to speak in more generalized terms and patterns (because of the Ne). Their warmth is more individualized in some ways, because it's coming from Fi (internal and thus personally expressive) rather than Fe (the external rule system defining what different acts "mean" relationally). They seem to judge people based more on their motivations, not necessarily what comes out.
Out of the two, in terms of interaction (which occurs in the external world), INFPs (using Ne) seem more flexible than INFJs (using Fe), who seem to be more self-controlled and have their world a bit more orderly and prioritized. In terms of control issues, INFPs seem to control their inner world and let the outer go more, while INFJs seem to like to control their outer world more.
Also, there is this thing called "revenge" that I see so much more in INFJs than in INFPs. I cannot really define it well yet, but INFJ dreams seem to be more violent and expressions of anger and retaliation and implementing "justice" against someone for the wrongs they have committed against them. It is like the INFJ has been prevented by Fe from acting on their anger, so it comes out in other ways; also, emotions have to be carried out in specific acts, implemented in some way.
The INFP can be gravely wounded by someone as well, but the judgment is something they carry around internally. Outwardly, they might fail to show or implement it, and even waver / show doubt about it. They tend to resolve the matter internally, rather than needing to extrovert it like the INFJ.
Note: In light of all this, it seems much better to piss off an INFP than an INFJ.
Note: These are just my first thoughts of some of the differences, and so they are prone to revision.