The possible causes of delayed menstruation with back pain include: 1, eating too cold food before menstruation, or using cold water for bathing, staying in a cold environment for a long time, etc., resulting in cold invasion of the uterus, causing vasoconstriction in the uterine cavity, and menstrual blood cannot be discharged, resulting in symptoms of delayed menstruation and back pain. 2, endocrine dysfunction of the ovaries due to various reasons, resulting in the endometrium not being able to timely 3, endometritis, pelvic inflammatory diseases, such as chronic endometritis, chronic pelvic inflammatory diseases and other gynecological inflammatory diseases, affect the normal proliferation and exfoliation of the endometrium, resulting in delayed menstruation, and accompanied by obvious symptoms of lumbago. The cause of this symptom is not exactly the same among different individuals. You can visit the gynecology department of a public hospital and undergo the necessary auxiliary examinations to clarify the specific cause before treatment.