Unless there is a Medical problem with the shoulder- sounds like a fit problem.

But I would expect a poorly set up bike to hit the back- hands and wrists first. The normal remedy for the hands is to bring the bar back and up. I say normal- but that is not always the way to go. But that is not the problem you have in any case- but it may be a way of alleviating the problem.

But there are many formss of shoulder pain. Is it the effect of an old injury from years ago? Is it musculatr or a deeper pain? Any of these are a trip to the quacks so elimate medical problems first.