what's this pain? So since about 10 weeks I've had horrible back pain at first I went to therapy for…

what's this pain?

So since about 10 weeks I've had horrible back pain at first I went to therapy for a work related injury and that helped but only for a little bit. Now this pain is in my mid-back and comes when I lay a certain way or move a certain way. The best way I can describe it is that it feels like I can't move as I get up. My back muscles feel stuck and I have to move super slowly just to get back up. I've mentioned it to my OB twice. The first time she said it was too early to be related to my pregnancy. The second time she said to put heat on it and take Tylenol when needed. What can it be? I feel like it's getting worse and worse. ?