Try to do things in moderation... eat a little fruit with a little grain with a little vegetable... at the same meal. Too much of anything might just be "too" much.

But that really isn't your real problem, that you don't like yourself is. You might be using your body and sex as an excuse for wanting to be "someone" else and not you. It won't matter what you look like if you won't like yourself anyway. I agree, find someone to talk to about these feelings. At the very least, being a journal or blog and begin writing them down so you can see what you are saying and what's going on with yourself.

Do you have a counselor through the school you can contact? The principal is usually available, even when school is not in session. Having thoughts of suicide is not normal, and not healthy as you know. You don't really want to end you life, I bet, but want your life as you are living it to end, to change. A therapist can help you do that.