I'm 15 and I'm having this excruciating pain in my right breast close to the middle of my chest. When I breathe in really deep it tenses up and feels like I'm being stabbed. It hurts so bad I can't force my self to breathe for 2-3 seconds and I turned over on my stomach and it actually provided some relief I can hardly feel anything now? Now I've turned back over on my back and it's completely stopped? What could've caused it?