(For some reason, people have told me repeatedly that I am INFP, but yet I don't think (from what I've read about Fi that) it applies to me; but yet I don't seem to recognize Fi when I see it in others. Is this because I don't in fact use it? Or Ti just seems more straightforward? Just a puzzling thought.)
I think you are too young to have really grow into your true type, whatever that may be. Once you are happy and well balanced in your life, comfortable with people and your social life, dealt with your procrastination and relationship issues, and found your path in life, then try to type yourself. Until then just look at the types and see what fits and what doesn't, and use the advice for the different types to solve your various issues. And don't take what anyone says too seriously. Only you know who you are.