Calm down. I've felt the same way as you in the past, and was diagnosed with an anxiety disorder a few years ago, and take it from me, you can't go on feeling this way. I'd talk to your school counsellor/mentor about the hair tearing, this is obviously a form of self-harm and you can't let it continue or it'll get worse. Are your parents aware of what has been going on?
Do as the others before me suggested - study a couple of topics per day for different subjects. Make sure you take regular breaks in between studying so you don't feel 'burned out' - I was once told that studying in small chunks, and then having a 15-minute break in-between does wonders.
Give yourself some time off. Like I say, I totally understand that you want to do well, and you're obviously very driven. But you need a bit of relaxation time every night. Read a book for pleasure, listen to some music, watch a movie, exercise - whatever!
Ultimately, you haven't ruined your chances at all - you sound like a very dedicated person who has worked themselves up a little too much.