Random Bleeding?

I’m not gonna post a picture but ever since I started my period it’s been clock work, never been on bc or anything. Always has been a 28 day cycle and randomly I am spotting.

I had sex 2 days before my ovulation day but we used the withdrawal method. I know it’s not reliable but it happened. About 6 days after we had sex I started spotting and it was brown and only when I wiped. Next day was a little heavier but not enough to fill a panty liner and it was like rusty brown.

I want to say it’s an early period but my period are NEVER brown in the beginning on at the end and like I said they are clockwork. I just want to hear what you guys think it could be. I’m stressed 🙃