Had period for 3 days, stopped, came back???? lol

Hi ladies,

So I had my period for three days, and then the fourth day I didn’t have my period at all. I had sex with my boyfriend and no blood was there, everything was super amazing. (The sex felt extra great for some reason too lol) so basically after we had sex I started feeling cramps and I was like hm that’s a little weird. When I woke up the next day (which is today) I realized my undies had blood, and when I peed, I peed blood again.

Has this ever happened to anyone? & is it normal? lol