Hello jonet
I am not sure how long you have had your device but if the surgery was fairly recently, you are probably still healing.
I, too, had a fair amount of pain/discomfort in my left upper arm after surgery. That lasted for about 2 weeks. Then it gradually faded. I have found that using a gel pack from the refrigerator, wrapped in a towel, and placed over the generator or on the arm in question, for 10 or 15 minutes, really helps soothe any discomfort. Taking Tylenol helps, as well.
My device is tacked to my pectoral muscle with a stitch to help keep in place. I hope my suggestion offers you some relief.
Best wishes.