6 Reasons Your Period Cramps Hurt so Bad—Other Than PMS by Women's Health If you're the proud owner of a uterus, you're likely well acquainted with cramps. But to understand why you get them in the first place, it's helpful to think of the uterus like a huge muscle (because, well, basically it is)—and it gets a pretty big workout during your period. “Uterine lining builds up over the course of your cycle, and the uterus responds with cramping as a method to control the bleeding [during menstruation],” says Christine Masterson, M.D., chief of the women and children’s service line at Summit Medical Group in New Jersey “If you have a lot of menstrual blood or a blood clot, sometimes the uterus will cramp to expel that.” How Gynecologists Soothe Their Own Period Cramps Most of the time, painful period cramps are super inconvenient, but pretty much NBD...until they're not, like if they affect your daily functioning, says Masterson. So how can you tell t...