You're growing up, and you're in school. I can tell you from experience (as I'm 16) that this is going to cause huge amounts of angst and anxiety like this, and it is COMPLETELY normal. Don't worry one bit about whether or not this is how you will spend the rest of your life, because you will develop so quickly in the next few years, change so much, and become so much more brilliantly intelligent and thoughtful that you will be a completely different person, with completely different wants, needs and troubles. The most important thing to realise here is that this tidal wave of confusing emotions, conflicting feelings and screwed up things that you can barely put into words is entirely normal for a teenager, especially an INFP.
School is going to make it difficult for you to be as happy as you once were, and so are your hormones, but it does fade away eventually. My advice would be to just make peace with who you are. Try not to worry, try not to obsess about yourself or your life, and just try to enjoy your free time. Whether that means being reclusive and not meeting up with friends, whether it means being a social animal, whether it means becoming a stamp collecting fanatic, I don't care. If it makes you happy, do it. Don't try to be the person the social extrovert society is forcing you to be, don't concern yourself with how happy the people around you are, and just lay back, relax, and let life take it's course. The next few years of your life are going to be emotionally tough, but you will make it through sure enough, and if you focus on just being the person you want to be and doing the things you want to do, then you will come out of these difficult years feeling better as a result.
I hope that rambling response helps.