Trying to figure out if it’s just an irregular period or what.

I gave birth to my first kid almost a year ago . I just started having periods again in June, so I’ve only had two. First one was fine. The July one was weird. I tracked it for about 12 days. During the 12 days it fluctuated: some days just spotting, then full on Game of Thrones.

I was supposed to start my period 6 days ago. We had unprotected sex about 3 days before my predicted period. No idea when I ovulated, I just started tracking.

I took a pregnancy test this afternoon, it was negative.

Is this normal?