Bleeding after sex?

So my period ended 4 days ago but today I had sex with a guy and a few hours later I felt a gush. I went to the bathroom and a quite a bit of blood came out? It wasn’t brown, it was red like new blood. I thought I was ovulating but is that still true if all this blood came out? I’m confused.

I had to put a regular tampon in because I’m still bleeding after my shower. Had some cramping. It’s like I just started my period all over again?