It could be that you are experiencing a condition known as "frozen shoulder". I believe the medical term is known as "adhesive capsulation".
Look it up on the internet. I had it four years ago in my left shoulder so bad that the doctor had to do surgery (it was called a "manipulation") on it followed by six weeks of physical therapy. The doctor first tried therapy on it to cure it, but it didn't help. If I remember correctly, there is a gel-like substance inside your shoulder joint that serves as a lubrication for joint movement and to keep the bone from deteriorating. In some middle-to-elderly people, this gel-like substance tends to harden, causing a loss of range-of-motion coupled with pain. I had a severe case of it and pain so bad, I could barely lift my arm. If I bumped into something and hit my arm, the pain would be excruciating. From what I can remember reading on the 'net on this condition, if left untreated, it will go away in 12 to 18 months.
During the 6 or so months I suffered with this condition, I got VERY adept at using the mechanical bridge.
Maybe you have an early or mild case of this condition???
Maniac