My DD (almost 13) has been having extreme breast pain for the last couple of days in her left breast. So much so that if anything makes any contact with it, it causes pain. I wasn't so worried, until she showed me last night, and the left breast was swollen, red and noticeably bigger than the other one. She hasn't started her period yet, and although her boobs do fit an AA cup, she doesn't tend to wear a bra. Should I see a GP? Does anyone have any idea what it is, other than puberty?