The pain in the uterus when the period comes is also called dysmenorrhea. There are many causes of dysmenorrhea, and the more common one is endometriosis. It is recommended to go to the hospital for an ultrasound examination, which can see if there are chocolate cysts or adenomyosis, which are all manifestations of endometriosis. The symptoms of dysmenorrhea in endometriosis are more pronounced, and this condition needs to be treated with medication or with surgery at the hospital. In addition, the cause of dysmenorrhea is uterine cold, the uterine cold is prone to stagnation of menstrual blood and poor drainage, which can easily lead to dysmenorrhea, in this case, you can take drugs to promote the discharge of menstrual blood and relieve abdominal pain.