Serious back pain

So lately I've been dealing with serious lower and middle back pain. It's a sharp and almost sore-like pain. It hurts to move, lie down, turn, and sometimes while breathing. I don't know what's wrong with me. I'm not pregnant, but I recently got off my period. I've been doing yoga in gym class, but that's suppose to relieve back pain. And for track we don't really lift that much. I'm not sure where it came from. It started about 1 1/2 weeks ago. Any insights?