What Causes Vaginal Bleeding For Every 5 Minutes?

Yesterday from 1pm onwards i was on the toilet every 5minutes i had severe bleeding from my vagina.. i also had alot of big blood clots that came away with it, it was that bad i could feel them all coming out, i couldnt even use tampons because they would last 2minutes, i nearly fainted and felt like i was out of breath most times, even if i laid down and got back up again i had many leaking episodes. Im very weak today and have to move around slowly, im very concerned at one point i had to lay in the bath in my clothes with the cold tap on because i didnt feel right, please tell me whats wrong?