M.N.
I have fibrocystic breasts and my breasts will get so tender that I can't stand for anywhere on my chest to be touched. They will also wake me up in the middle of the night because they are so tender. (I have approximately 100+ lumps in each breast and they will swell to the point where you can see them through the skin)
Try laying off the caffeine (chocolate has caffeine in it too) and maybe try an ibuprofen to help with the tenderness.
I also have breast cancer in my family. However from what I have been told cancer would not be causing the discomfort.
It never hurts to get it checked out but I am thinking it is more of a hormonal thing. Good luck!!