You need to talk to a counselor. This is not something you can handle on your own. And the longer it goes on, the more damage you will do to your body. We're talking about *permanent* damage, and it will affect you for the rest of your life. This isn't just an innocent thing to lose a bit of weight, this is neglecting your body of the nourishment it needs to keep you moving, breathing, thinking. It will find that nourishment somewhere, even if it has to break itself down. This damage is not reversable.
You should try to concentrate more on getting help on this and less on dieting. I know that's hard because it's all you think about, but you *need* *help*. And you need it now. Talk to your school counselor, or maybe a teacher. They can put you in contact with someone that can help you.