Help?

So I took plan B last Tuesday after having unprotected sex Monday and I had no side effects or anything until Sunday night.

I started having really bad cramps and I got a heavy flow yesterday and it hasn’t gone away.

I had seen on the internet that spotting was common, but bleeding this much just like I do when I’m actually on my period is scaring me a little.

And btw it can’t be my period because my last day was about a week and a half ago.

Is this normal?