Is it stress?

I haven't seen my PERIOD since September 15-19 2019. My app told me I ovulated On the 28th. I had sex October 1st & Spotted October 30 & 31st. I took a pregnancy test In January which was Negative. My Nipples get really sensitive before my Cycles comes. So I had that symptom but My PERIOD still haven't came yet. I have irregular Periods. But this is the longest I've gone without it.

Any suggestions? Similar Problems?