Can you really have periods and still turn out to be pregnant? Not spotting, like proper bleeding... If so does it go through your whole pregnancy or does it stop?

Like how to you know if your pregnant if you still get your period? My test was negative?

There are girls on here that say you can have your period like bleeding and negative tests and still be pregnant. I'm so confused.

How do you know if it's a period or just bleeding?!