It may be related to the hormonal changes in the body. Before the menstruation, there will be small stomach pain, back pain, general weakness, irritability, etc. This is premenstrual syndrome, no treatment, you can observe, menstruation early or delayed a week are normal. Pregnancy can cause delayed menstruation easily cause abdominal discomfort, breast swelling and pain, the symptoms are similar to the symptoms of menstruation, if there is gynecological inflammation can also cause, such as having pelvic inflammatory disease, endometritis, etc. can also cause abdominal pain, lumbar discomfort, etc. You can go to the hospital for ultrasound examination. If it is determined that there is pelvic inflammatory disease can take gynecological Qianjin tablets, if the endometritis can be treated with antibiotics, you can take amoxicillin, it is recommended to pay attention to hygiene.