Could endometriosis cause 17 day period and heavy flow at night as well as extreme pain at night?

Endometriosis pain ?: Endometriosis can cause pelvic pain with menstruation, but heavy flow for "17 days" does not come from endometriosis. If pregnancy is possible, obtain a serum HCG test, and if positive , see your gyn immediately, as a pregnancy outside the uterus (ectopic) can certainly cause this kind of bleeding. If negative, schedule an exam with your gyn for additional testing.