May be mastitis,cyclical pain,breast cysts, breast trauma, prior breast surgery or other factors localized to the breast. Breast pain may also start outside the breast... in the chest wall, muscles, joints or heart, for example Cyclic breast pain appears to have a strong link to hormones and your menstrual cycle. Cyclic breast pain often decreases or disappears with pregnancy or menopause...consult nearest surgeon they will help you if its not cyclical one..

Probably fibroadenosis or Premenopausal syndrome.  But you should get yourself examined by a doctor to rule out anythong else.