The reasons for not having a period but pain in the small abdomen and breast pain are as follows: 1. The most common reason is due to fluctuations in the level of estrogen in the body, which can lead to menstruation in 1-2 days after the appearance of these uncomfortable symptoms; 2. Some pregnant women may also experience pain in the small abdomen and breast without a period, mainly due to the increase in the level of estrogen in the body after pregnancy. Therefore, early pregnancy monitoring can be performed in time to avoid accidents and ectopic pregnancy; 3. Reproductive system diseases, which lead to discomfort without menstruation, are most common in acute pelvic inflammatory disease, mainly due to local pain caused by pelvic congestion and edema, and reproductive system diseases can lead to endocrine disruption, resulting in breast pain. The symptoms can be properly relieved by more rest and self-regulation.