You really do need to talk to someone with some expertise.
If you don't have a trusted friend to talk to, try talking to a counsellor.
Self harm is very serious and if you're ruining your chances of doing what you love best you will come to regret it as you get older.
Rubber Fish Anonymous Advice This is my friends website, she is a trainee counsellor and is really helpful, she will answer your problems straight away and talk them through with you.
I hope she can help, or you can find someone to help.