Period is late by 12 days

Should I be worried ? The last time i had sex was back in October. I took a plan b right after sex I know he didn’t finish inside me however the condom did pop so I took extra precautions. A few days after the pill I spotted for a few days. And now it’s November and I haven’t seen my period I’ve take several tests and they’ve all come back negative with no faint lines. Has anyone else experienced this before? Looking for some advice...