Most girls and women will feel some change in the body before, during, or after their periods. When the blood lining is released out of the body, the abdomen area will squeeze that causing stomach pangs or cramps. Many girls also experience backache, headache, or weakness. But it is fairly normal and part of the process. If you are experience severe cramps, which interfaces your daily activities, and accompanied by heavy bleeding or clotting, visit your gynecologist immediately, as the pain may be associated with severe other health conditions like endometriosis, PCOS, etc.