I havent had a menstrual cycle in a year and a half and i started bleeding heavily the last three days i cant stand the pain i take something and it doesnt help?

At your age with this history & severe pain you definitely need to see a Dr for full evaluation, including a pregnancy test, tests for infection, & possibly an ultrasound. Post menopausal bleeding (bleeding after more than a year without menses) must be thoroughly investigated- call your Dr or go to ER ASAP.

This is something that definitely needs to be evaluated by a gynecologist .any bleeding that occurs after ceasing for a year has to be checked with a sonogram and most likely a procedure called an endometrial biopsy where are you get a sampling from inside the uterus to evaluate for causes