The back pain that occurs when menstruation is delayed for four days is considered to be premenstrual syndrome, which occurs when menstruation is delayed due to the influence of mental factors, the external environment or diet, resulting in the poor discharge of menstrual blood. When menstruation comes before, due to changes in the body’s hormone levels, some sensitive women will appear back pain, abdominal pain and discomfort, is a normal phenomenon, do not need to be particularly worried. It is recommended to take a good rest, keep a good mood, eat a reasonable diet, pay attention to the small abdomen to keep warm, and get ready for the onset of menstruation. If you have regular menstruation and your period is delayed for more than 3-7 days and accompanied by back pain, consider the possibility of early pregnancy. As the egg and sperm will be deposited in the uterus after the union, which will stimulate the surrounding organs and lead to back discomfort, it is recommended to take blood tests for human chorionic gonadotropin (HCG) and ultrasonography to ascertain whether you are pregnant or not.