Breast pain is very common in women of all ages. It can be caused by hormonal fluctuations, fluid retention, changes in breast tissue, or a variety of other factors. Hormonal fluctuations are the number one cause of breast pain, with breasts becoming sore three to five days prior to the beginning of a menstrual period and sometimes continuing through the end of the period. Other causes of breast pain include breastfeeding, using a breast pump, being near ovulation, and wearing a bra that doesn’t fit properly. Additionally, some medical conditions, such as mastitis, fibrocystic breast changes, and breast cancer, can also cause breast pain.