The presence of stomach pain before menstruation does not necessarily mean that you are not pregnant in clinical practice. The reason why stomach pain occurs before menstruation may be due to the following reasons First, chronic pelvic inflammatory disease, either after pregnancy or before menstruation, can lead to congestion in the pelvic cavity, so it can aggravate premenstrual stomach pain. Secondly, endometriosis and pelvic tumors may cause stomach pain before menstruation. If the sperm and egg have already united to form a fertilized egg, most of the fertilized eggs have not yet been laid before menstruation, so stomach pain is often not related to pregnancy itself, but to the primary disease. If you are not pregnant by the time you get your period, an early pregnancy test, or a blood test for HCG, can help you find out if you are pregnant.