If a woman has pain under her belly, it may be caused by gynecological diseases, such as gynecological pelvic inflammatory disease, pelvic tumors, endometrial inflammation, endometriosis, and after pregnancy, pre-eclampsia may also lead to pain in the belly, and when menstruation may lead to dysmenorrhea, which may cause serious pain in the lower abdomen. If you have an intrauterine device, the ectopic stimulation of the device can cause contraction of the uterus, which can also lead to pain in the lower abdomen, so you should go to the hospital as soon as possible for an examination and give the appropriate medication for treatment, taking into account the clinical history. If there is pain in the small stomach and diarrhea, it may be caused by gastrointestinal diseases, so it is recommended to go to the gastroenterology department for treatment in a timely manner.