Weird bleeding...

Around this time yesterday I had way way heavy bleeding, I mean completely out of nowhere. I was laying down and when I got up it just gushed out everywhere. I'm like okay great started my period, even though I never start like that. I go to bed, and I bleed throughout my sleep, get up and get ready for work, and put a tampon in. By the time I get home and take it out there is nothing on it. Ive never been regular unless on BC. I usually skip months and be on it anywhere from a week to a whole month. I also don't get cramping often at all and nor do I pms, do I don't have any signs that I'm about to start really. I haven't had a chance to know my body like that. So I have no idea what this random bleeding could mean. Any ideas?