I had a breast biopsy last Wednesday, March 26th. US guided and vacuum assisted. Benign results thank God, no atypical cells either, and I was pleased that compared to the other biopsies I have had in the past (MRI guided, CORE needle, Sterotactic, and Surgical) it seemed to not hurt all that bad. Now 12 days later I have my period and the pain in that breast is killing me, also under my arm a little, I think. Maybe because I lift a 25 pound baby all day it has something to do with it! But how come as soon as my period started, it started to kill?