The swelling of the breasts before each menstrual period is mainly due to hormonal changes in the body that stimulate the breasts. Menstruation is caused by the combined action of estrogen and progesterone in the body. Before menstruation, these hormones undergo certain changes in the body and reach a high level when they stimulate the mammary glands, resulting in congestion and swelling of the epithelial cells, which can cause mild swelling and pain when the breasts are touched. Most of this pain is tolerable and will recover naturally after menstruation, which is a physiological change and does not require special treatment. If the stinging pain is more obvious and there is a lump to touch with your hand, you should consider the possibility of breast disease and suggest going to the hospital for a mammography examination.