Many people experience pain alongside their period. The medical term for this pain is dysmenorrhea, which is split into either primary or secondary types. Primary dysmenorrhea is the usual pain that comes just before or during a period, not caused by any health condition, whereas secondary dysmenorrhea is caused by an underlying problem, such as endometriosis. The pain can be felt as anything from dull achy cramps to intense sharp pains.
During a period, muscles in the wall of the womb contract more to help the lining shed. These contractions compress blood vessels, temporarily cutting off the blood and oxygen supply to your womb. Without oxygen, the tissues in the womb release chemicals that cause pain.