Most of women, especially young ones, are experiencing breast pain that radiates to the arm pit, exactly at the time of menstrual period.
This pain is worse before the menstrual cycle and usually is relieved at the time period begins. It may also happen in varying degrees throughout the cycle, and because of association with menstrual period is known as Cyclic mastalgia (algia means pain, mastos, means breast).
The reason for this are hormonal changes before and during menstrual period.

First MandMS....love new avatar...what an adorable little girl Got to be your daughter!! As for jam_geum, MandMs is a whiz at medical jargon and knows her stuff........if its something medical, she's the gal to ask! Sorry I can't help. HUGS!