Hi there,

Just from looking at your pictures your scapula's are winged. I think some serratus anterior and lower trapezius exercises would be quite helpful to help hold that scapula against the thoracic cage. Your scapula look slightly abducted so some rows using a resistant band can help with that to get proper retraction happening. The pain is no doubt connected to the scapula position and function during movement. I'm sure one of the physio's on here will be able to offer better advice, however I think it may be beneficial to get it assessed by a physio.