Pain In The Arm Due To Excessive Exercise. Heavy And Sore Breasts With Red Patches. Is The Arm And Breast Pain Linked?

I have had a pain in my left arm for about 5 weeks, which I have put down to over stretching in an excercise class. The pain has gone from my upper arm down to my elbow, and I have often had to 'hang' my arm out of the bed to relieve the pain. On Wednesday this week I felt my left breast was very sore, and by yesterday had increased in size to almost double that of my right breast. It feels heavy and sore, and the pain is familiar to that of when I was breast feeding and my breasts were full of milk. On looking today, my left breast looks like it has a red patch over it. I am in a lot of discomfort. Are the arm pain and breast changes linked? I am a fit and healthy 50 year old, size 10, and very active. I do not smoke.