Strange back issue..

So, I have this horrible stretching pain in a muscle starting around my shoulder blade and running down the right side of my back. The only relief I get is when I press it against the corner, or if I lay against a little lacrosse ball and roll it up and down. But, when I do this, baby immediately starts moving around. I'm trying so hard to figure out what is causing this pain and why when I press on that muscle, it seems to trigger the baby's movement.