I'd suggest visiting a sports-injury doctor, because a few years ago I injured my rotator cuff while working out a few years ago, and I found the injury very odd in that the pain was very inconsistent - It would hurt one minute, and not the next, and the next minute it would hurt again... and I...
I have a similar problem - I constantly sprain the same ankle when running after a very bad sprain a few years ago. I've been thinking that a bosu ball might help. Haven't tried it yet though.
Justin
www.GoalPosting.net