Hi---it sounds as though you may have a rotator cuff tendonitis----what we commonly refer to as impingement syndrome.
Visit this link for more information and an informative video at the bottom:
http://www.rearmyourself.com/article...ement-syndrome
Typically, a 6 week trial of physical therapy will improve things. That's where I'd start!!
Let me know if you have any additional questions. Visit the PT section on
www.rearmyourself.com and visit one of the PT providers listed!! In New York State you can self refer yourself and receive treatment for up to 4 weeks without having to see a physician first.
Matt