Clavicle pain

I have been doing Iyengar yoga for 7 years to help with degenerative disk disease and arthritis in lower back–it has done wonders(I can do backbends and twists etc.). Recently I was diagnosed with the same problem in my neck and am currently having physical therapy. However, for 6 months I’ve been experiencing chronic (and sometimes acute) pain in my right clavicle, close to the sternum. There is definately a difference in appearence (it juts out further and is larger) between the right and left S/C joints. The pain is much worse after neck therapy. Since the x-ray of the clavicle showed no breakages the doctors seem to be ignoring it and treating it as part of the neck problem, but I feel it is unrelated. Obviously I stopped doing head stands once my neck began bothering me. Since one has to press down very hard with the forearms and elbows to help keep the pressure off the head and neck, I’m wondering if this posture over the years may have resulted in a slight dislocation or injury to the S/C joint–or is this just plain old arthritis at work(I’m 62!). Thank you–any input will be appreciatedDiana