I am experiencing pain under and behind my left breast and between my left ribs. the pain even moves towards my back (left side). i am 11 weeks pregnant. what could be causing this?

Pregnancy hormones: During pregnancy you begin to make a hormone called relaxing, which causes relaxation of the tendons, ligaments, etc at your joints. It's meant to relax your pelvis to allow delivery of the baby. However, it affects all joints including joints between your ribs - yes, there really are joints there. I suspect much of what you're experiencing has to do with this hormone.