No period and negative pregnancy test

I’m 6 days late. I’ve taken 3 pregnancy tests at different times of day, all have been negative. Nervous/paranoid as to what is going on….

Normally my period is very regular every 28days and last 4 days. I was on IUD for 2 years, got it taken out 3 months ago, currently back on the pill.

Since then nothing changed. My periods continued to be normal (every 28 days for 4 days).

** I have a doctors appointment for this coming week but I figured I would ask here if this has happened to anyone before.