I used to do a high bar placement but a while back I switched to low bar. After doing low bar for a while a muscle in my back near the left shoulder blade started to hurt. I stopped squatting for a month and I tried again today with only 135 lbs and it hurts again. Im not sure what I could be doing wrong. I do tend to stick my head out and its possible that i might have some upper back rounding. Could this be doing it?