March is endometriosis month. Nearly one in 10 women experiences endometriosis during her reproductive years. Endometriosis occurs when the tissue that normally lines the uterus is found outside the uterus, normally in the pelvic cavity. One of the biggest symptoms is pelvic pain. One third to one half of women with endometriosis may also become infertile. If your menstrual cramps are severe month after month, then you should speak with your health care provider about the possibility of endometriosis and finding a treatment plan that works for you.