I would get a mammogram. I really hesitate to tell you this but I had strange feelings in my breast for a long time and it did turn out to be breast cancer. The way I can describe it to differentiate it is that unlike period/hormonal breast tenderness I felt like I could pinpoint the exact spot/s specifically. And it was kind of tigly.
One of the BIGGEST myths of BS is that it doesn't hurt and you can't feel it. If you are young your doc may hesitate to get you screened-I would insist if I were you. The age of onset is getting younger and younger unfortunately and many docs still don't take it seriously.