Testing negative after 9 days late

Help!

I was supposed to start on Dec 26th. My cycles always run 28-29 days... I’m about as regular as can be. Today, I’m 9 days late, and tested negative. I’ve had very mild cramps throughout these 9 days, I’ve had evening time nausea 4 days in a row and I’m super emotional.

My plan is to call my dr Monday, and see what to do next. Has this happened to anyone? I’ve never not had a period, nor had a period that was this late. Any help is appreciated!