Bleeding?

ok so we’ve all heard stories about how someone has had a ‘period’ throughout their pregnancy however research states that can’t happen. so it would be so other type bleeding like decidual bleeding. I have heard decidual bleeding can come right about the time u would normally have your period and mimic it. But how heavy is the bleeding actually? Like is it similar to implantation bleeding or is it enough blood to be able to use several tampons throughout the day? Has anyone has heavyish bleeding and but actually been pregnant? Thanks