I Havean Injury To My Shoulder From Straining It Trying

I havean injury to my shoulder from straining it trying to pull something heavy it has been over qyear and seems to be getting worse.i hadxrays nothing showed,a shotof anathetic/cortisone nothing helped.went to physical therapy ten times no help ther ether.now I also have no strength in my arm.with constant pain however I can rotate my arm freely I am scheduled for an mri mon. I hope this willshow something it is painful23hrs a day