If you are doing self harm, like biting to relieve stress, it's really important you talk to someone. You are only 16 and this is a shock to you. You said you have new bruises and bites, so I'm suspecting this isn't the first time you've done that. Can you see your family doctor, or call a teen hotline? It would be at least something more local, and because you are underage there are programs that can help you okay? Once you become 18 it's a whole different ballgame. Check in your white or yellow pages for teen hotlines, they are always in the front of the book. Do you have a counselor already, or could you go to your school's counselor?
I'm also going to give you a link for the teen depression forum, it might be a bit better for you.
http://www.medhelp.org/forums/show/185
Like bulldozer said, it's better to hit a pillow, scream or anything then hurting yourself right? Eventually your marks could become permanent, and later on, you'll feel better and really regret doing them. Hang in there, it does get better!