Bleeding not sure if it’s af

My period was on and off the 25th and 26th and it ended it was an average cycle for me. Then I had sex Saturday (with protection) and I ended up bleeding a lot. I mean a lot. It didn’t hurt and ended quickly so I wasn’t THAT worried but then I got up this morning and used the bathroom and there was more blood. I’ve had periods that stop and start back up. Maybe it’s bad timing. Anyone know what it could be?