Pain from armpit to behind nipple

I've had pain since June 2017 with the lumpectomy and right total axillary clearance. The pain was initially in my right armpit to my waist and down right arm to elbow. Plus pain in breast from scar tissue. I am now on only two Panadol a day rather than 6.  Recently the lump under my lymph node armpit scar got warmer and more pronounced. The GP could feel the lump and said it felt like a lymph node...though supposedly all removed. I had an ultrasound and all clear. (I was pretty fed up with the thought that it was something sinister as my treatment lasted 16 months.) I don't seem to get the pain to my waist anymore. Since I started light weights for half an hour twice a week my pain in the arm has reduced dramatically over only 4 sessions! But I would get it checked out for peace of mind.  We all need some of that and less stress. It's the first time I have worried about recurrence so I feel or felt totally shocked. Xxx