I had an expander inserted following mastectomy. My surgery was Nov 27, 2021. It's been about 6 weeks for me. I experienced the same discomfort as you, but it gets better! It's feeling so much better now. It's uncomfortable for two days following addition of saline, but not too bad other than that. I hope it gets better for you!
I am 8 weeks post op DMX with expanders. The side that didn’t have multiple lymph nodes removed is fine. The cancerous side is very tight and swollen and woody and skin is pink, sometimes red, but no infection. Gets very painful especially in the evenings. Cold compresses help, not ice. Yesterday my RMT working on my scar tissue and lymph massage worked on that breast and it helped to soften it up. But the “normal” side definitely felt better a month out from surgery, just needs time. Pretty invasive to put pressure on the muscle for sure. Definitely tighter for a few days after saline injections. But it gets better. The lymph side, for me, I can only hope gets less painful! 7 months before they get removed as i will be going thro radiation next.