As all4 of my dads sisters ahve had breast cancer, 1 of whom died with it.
Anyway, its on the left side, on the outside, very painful, but oddly not as painful when I have my bra on. I can't feel any lumps or bumps, but when I press on a certain area its very painful. if i move my arms certain ways such as above my head, or out to the side it hurts