What are the causes for extreme menstrual cramp pains?

Variety of reasons: Cramping occurs due to formation of substances that cause smooth muscle contraction. Nsaids like advil (ibuprofen) etc block the formation of these substances which is why they can help with menstrual cramping. However, if cramping is severe, more serious issues may be lurking. If menstrual cramping is affecting activities of daily living, an evaluation is in order.

Menstrual cramps: Reasons for significant menstrual cramps can be endometriosis, cervical stenosis, uterine fibroids, adenomyosis ; pelvic inflammatory disease.