She wants to spend every minute with you because she is extremely insecure, but it isn't healthy and you should definitely set some boundaries. You are hanging out with her WAY too much. Don't you guys have homework to do? Tell her you need to stop spending so much time with her or you need to break up. She is supposed to enhance your life, not monopolize it entirely or prevent you from having other interests. Be firm about it, and mean it when you say it.
Relax... I'll need some information first. Just the basic facts - can you show me where it hurts?