Normal menstruation varies from woman to woman, but is typically described as a period every 28 days that lasts for 2-7 days. Abnormal menstruation, with endometriosis, can mean anything from irregular and unpredictable periods, heavier than usual bleeding, painful, or bleeding between periods. There may also be large clots in the menstrual blood. Abnormal menstruation could include any combination of those, including just one or all.Abnormal menstruation can also be caused by pregnancy, stress, menopause, excessive exercise, some medications, and many other medical conditions. A single abnormal period by itself may not indicate endometriosis, unless other symptoms are also present.Next