Menstrual cramps are caused by contractions in the uterus, which is a muscle. The uterus, the hollow, pear-shaped organ where a baby grows, contracts throughout a woman's menstrual cycle. If the uterus contracts too strongly, it can press against nearby vessels, cutting off the supply of oxygen to the muscle tissue of the uterus. Pain results when part of a muscle briefly loses its supply of oxygen.

I am feeling like, really. Nothing seem to relieve my belly's pain. Ouch...