I have been to the Chiro about it. The guy that I normally go to that works a lot with our high school football team is the one that said bicep tendonitis. He is really good but he has had some serious health issues and has not been able to work much the last few months. I went to another guy that I know and he just said shoulder tendonitis. He is who I have mostly seen with this. He has given me the ultrasound treatments and told me a series of stretches to do. They have helped but I still have the problem. The last time I went to see him I told him about feeling it move a little and he was not that concerned about it but I think, like you, that it may be time to get an MRI and get a better look at it.
The trainer for our football team works with the bone and joint doctors nearby. If I say something to him he will get me in to see them a lot sooner than if I just call their office. I think it just may be time to take that step.