Late period but negative pregnancy test

I got my IUD out on 12/4 then had a surgery to remove a urethral diverticulum on 1/24 that required several weeks of recovery. Since all of that my I have been having roughly 24 day cycles. My last period was 3/4 through 3/7 and we did the deed on 3/15 when I supposedly ovulated. My next period was supposed to start on 3/27 but it didn’t. I’m going on 6 days late and still no sign of my period.

I have taken 3 pregnancy tests and all have been negative (1 a couple days before missed period, 1 the day of missed period, and the last one this morning). So my question is, have any of you missed your periods and is this common?? Am I testing too early??