AF is 5 days late and then we had sex

AF is 5 days late. I’ve taken four tests and they have all been negative. This afternoon we had a kid free minute or two and we had a quicky. When we were done he said “oh look you must’ve started” I was relieved and sad at the same time (we aren’t planning for another one but aren’t really preventing it either) I went to the bathroom to wipe and there was blood. I put in a pad and we went about our evening. I go back to the bathroom before bed and the pad is clean and there is no blood when I wipe.

What is going on here?