Late period.

This is a bit of long story. On the last week of November I got my period while on the IUD. My period ended and the following week and that's when I got my IUD removed because my husband and I want to try for baby #2.

The day after I had my IUD removed I believe I started another period. It lasted 8 days. I tracked my period in November and the one after my IUD was removed first week of December. The app shows that I was supposed to start my period on the 2nd of January.

I am now 2 days late. I've been feeling cramps, nausea, upper back pain, and fatigue. I took a pregnancy test and it was negative. I've never experienced nausea or back pain with my periods before. I'm usually very regular. The last time I was late on my period I was pregnant with my first.

Has anyone else experienced something like this? What do you think I should do? TIA!