If you have a history of sexual intercourse and are not using contraception, and if you have delayed menstruation and lower abdominal pain, it is recommended that you go to the hospital for a timely checkup. The main purpose is to find out if there is any disease related to pregnancy, for example, if it is due to ectopic pregnancy. It is recommended to take a blood test for HCG and if it is positive, it is recommended to take another test every other day to find out if the delayed menstruation and lower abdominal pain are due to ectopic pregnancy. In addition, if endocrine disorder may also cause delayed menstruation, but it often does not cause lower abdominal pain. Delayed menstruation and lower abdominal pain may also be caused by pelvic tumors, such as ovarian cysts, which may cause this symptom, so promptly go to the hospital for examination and, if necessary, ultrasound to rule out the possibility of tumors.