what is going on with my period??

Veronica • 28 🇵🇷• Proud Mommy of 2 princesses • Married to the love of my life • TTCing after loss
My period was suppose to start on 9/15. I put a tampon in just in case. The entire day I wasted like 5-6 but towards the end of the day I started very very light spotting like 1 or 2 spots in the tampon and it was brown.
So yesterday same thing. We had sex to try and bring it on. And still nothing. Just spotting and now it's just brownish pink but very little. I am confused. I'm never late. I've taken 2 test from dollar store and both BFN
Maybe I ovulated late ? Has anyone experienced this?