You need physical therapy.. but I wouldn't guess.. ask surgeon. go see him.

Lymphedema can always develop months to years after breast cancer surgery, radiation or chemo. I would contact your dr and ask for a referral to a physical therapist that specializes in lymphedema after breast cancer. It has helped me huge! And I developed lymphedema 2 years after breast cancer surgery. Hugs and prayers.

frozen shoulder ? talk to your MD

Frozen shoulder usually presents as a pain in the biceps when moved at a certain angle. You could probably benefit from PT, regardless.
I waited for months to talk to my PCP. By the time I started PT I could not put away my dishes or comb my hair.
The good news is that I was referred to a PT specializing in BC patients. I cannot say enough good about her.
Today I have as full a range of motion as I can have with most of my pectoral missing. The cancer had deep tendrils so they had to dig deep, even into the chest wall.
I hope you get prompt results
Best wishes!

I remember when my under armpits was hurting me. I use to sleep with a pillow under my arm which help me a lot. and when I am just sitting around I be hugging the pillow