There are many reasons why your breasts may feel swollen: 1. During pregnancy and breastfeeding, two special periods, the body’s lactogen rises, resulting in breast milk production, the breasts will feel swollen do not need to worry, is a normal physiological phenomenon. 2. Mastitis, such as breast duct deformity during lactation, milk stagnation produces mastitis or nipple rupture, bacterial retrograde infection leads to mastitis. The inflammation will produce pus, which will make the breast swelling and pain. The actual fact is that you can get a lot more than just a few of these. 3. premenstrual syndrome is influenced by estrogen in the body, breast swelling, tingling, nipple swelling and pain can occur before and during menstruation. If the pain is not obvious, it will not be treated. 4. Breast diseases, such as breast enlargement or breast cancer, will have breast swelling and pain, and need timely treatment.