You should follow-up with you doctor. Heavy bleeding like that is unusual and there's usually an underlying cause. In a rare instance, it could be a miscarraige, even though your tubes are tied. You could also have a hormonal imbalance or fibroids which can cause unusually heavy and painful periods/bleeding or endometriosis. In any account, your doctor needs to evaluate the cause though.
You can get pregnant with your tubes tied, that's how I was conceived.
Kind of sounds like a miscarriage.. sorry if it is.. I would urge you to see a doc to rule out anything dangerous! I don't think you will be pregnant but we couldn't tell you that anyway. You will need to take a test. I hope you find out soon what's going on!!