I think that the heating pad might help a lot. Mastitis, you need antibiotics. I got it when I was new to nursing & my daughter was a few weeks old. I recall using a breast pump on the one breast that was affected by the infection. I also got put on antibiotics that very day and within a couple of days, I was all better and nursing with both breasts again.

Are both of your breasts affected? Are your breasts engorged? Hot to the touch?

I didn't know that it was possible to have mastitis without baby involvement. Hmmm ~ I do also recall developing a hard and sore breast (in a couple of spots) when my youngest daughter was 3 or 4 years old, so it had been 2 or 3 years since I'd stopped nursing. It bothered me for a while. I got an x-ray, followed by a mammogram. The mammogram squeezed so hard, the areas of dried milk(?) were crushed & the hardness disappeared. Weird!

(((hugs))) Hope that you find some relief to end your discomfort very soon!