There are many changes that happen during the menstrual cycle to prepare a woman's body for pregnancy. Breast pain that comes and goes with relation to a period is called "cyclical breast pain," and is extremely common. This occurs because of hormones that stimulate hyperplasia, or growth, of breast cells involved in milk production and delivery. Many hormones are involved in regulation of the body. During a normal menstrual cycle, the breast is stimulated by some of these hormones to prepare for lactation. When a woman does not become pregnant, the absence of these hormones then causes the breasts to involute, or return to a resting state. As long as the tenderness you describe comes and goes with your periods, it is most likely related to the routine variations in the hormone levels in your body, but should still be discussed with an OB/GYN or primary care physician
in his or her office. It is also important to have a routine breast examination by a licensed practitioner who will be able to tell you if there is anything concerning about your specific symptoms. Finding lumps or bumps in your breast, nipple discharge, skin changes, or a family history of breast cancer would all be important to discuss with the appropriate physician as well.
Pain that is not related to a menstrual cycle is often related to other causes, including infection, medications, large breasts, diet/activity, or pain referred to the breasts from other sites (such as the chest wall).