Breast health question?

I had a mammogram in April of this year, a follow up from one done a year ago for a painful mass on the bottom of one breast. Both mammograms came back normal.
Recently, I noticed that the breast I was having trouble with seems to indent or go concave (for lack of a better description) when I raise my arms above my head. I don't feel anything different when I do my BSE, but I'm just paranoid that they missed something. What could this be? I have a 9 month old baby, but I only breastfed for a couple weeks because my milk wasn't sufficient for him. Could that have something to do with it?
I know I should go back to the doctor, but I hate going back for another mammogram when I just had one (my insurance is already prickish about a lot of things like physicals, etc.).

This is not to be fooled with or ignored. You have to see a doctor. mammos do miss things. If necessary see another doctor - but do see someone ASAP.

has the doctor looked at it at all since this happened? if he recommends more tests the insurance has to pay.