Pain under breast and back!!!

I'm having the worse pain under my breast area and in my upper back. It hurts so bad that I'm thinking of going to ER but I hate the ER and don't wanna go if it's normal. I'm 16 weeks and don't remember this last pregnancy. Yesterday I worked 5 hours at my part time job and I did a lot of walking and getting up and down at the store talking to customers. Could this be why? I came home and slept from 6pm to 12am and then was up off and on all night in pain. Now the back is what hurts the most. Has anyone experienced this? I read online that it could be gallbladder issues.