Hi JoAn, It could be scar tissue. You could call your doctor and ask if he or she thinks you should come in before your scheduled appointment .

By the way there are massages you can do that might be helpful. I don't know if they work or not but you might want to try them to see if it makes a difference.

Ot could also be swelling from a seroma. I've had those twice and they aspirated them.

I would call the breast surgeon’s office on Monday and ask to talk to the nurse or NP and describe your symptoms and when they happen. Ask if there is anything you can do and if you need to be seen.

Do not wait to call as they can quickly resolve this.

I had a lumpectomy last February and since when I move or stretch a certain way it feels like a muscle pull. Very uncomfortable for a few seconds. Since it only happens occasionally I haven’t spoken to any of my doctors.
Your’s sounds a bit more severe though. I would probably start with the surgeon who did the lumpectomy.

Best of luck!! ❤️