Could something seriously be wrong?

You really should see a gyne right away before you lose too much blood. You could have uterine fibroids that bleed out. I don't know your age but that is what it sound like to me. And you need to do this quickly. A thyroid condition would make you tired if it were underactive but not make you bleed. You could have a serious gyne problem. I urge you to see one soon.