Yes I get this a lot and always on the left side and near to the nipple but I tend to sleep on my left side and I have large, droopy breasts and I think my nipple gets squashed when I'm asleep! I also have neck problems and get a lot of tight muscles.
Ibupofren helped the breast pain. It does come and go and I haven't had it as bad lately but at the time, it was really painful. I have had a mammogram since I had the pain and all was clear.
My Mum also kept getting pain in her left breast and the Dr told her it was muscular but she did refer her to the breast clinic and all was well.