Hi @Angel61. Sorry to hear this has started. I had my treatment around 3 years ago. Doing great with range of motion for about the 18months. I had kept up my post surgery movement exercises for around 9 months. I did develop lymphoedema very early, both arm and breast, so put a lot my discomfort down to that. My lymphoedema physio has been working on my shoulder for the last 12 months. I have stretches and exercises to do, generally keep my movement going. The areas you have pain sound identical to mine, which my physio has long said was from radiation damage. Maybe look up the Australian Lymphology Association website, see if there is a therapist in your area. I wouldn't trust anyone who doesn't have a good understanding of lymphoedema risk touch my shoulder, as they could potentially do more harm than good.
Take care