Jarebear, hang in there! Take a moment and just think about how loved you are (yes, you are loved), think about places you like to be and imagine yourself there. Write down all the things that are bothering you, write about the urge to hurt yourself, and get everything out. Then rip up the paper, or keep it to remind you of all the things you aren't going to let control you. Remember that your body is a beautiful, complex, functioning creation and you do not, under any circumstances, deserve to be hurt, physically or otherwise.
Do you have a T or a p-doc? If the urges get worse, try to see one of them. If you don't have one, talking to a school couselor can help (sorry, didn't look up your age). If you need more help, please don't be afraid to get it!
Hope something I said will bring you comfort and well-being.
Katie