Hi there, seems like you have issues resulting from previous injuries. Have you ever considered muscle function testing? http://www.bio-mechanix.co.uk/ is in Scotland and does MAT (muscle activation techniques) which helps re-activating muscle function. If injured your body compensates using other muscle (muscle groups) to keep you 'functioning' and starts overuse of those muscles that are not ment to be the 'main movers'. with shoulder girdle injuries it is a lot more complex as there is most likely more than just one muscle / tendon involved. Being extremely sore after having been shown optimal (correct) movements could be a sign for it. Hope, this helps