Irregular cycle? Missing a period? Ideas? Help?

Hi,

I’m 27 years old and me and the hubby decided to start ttc last year.

I always had irregular cycles and when I was around 18 I started taking the pill to make my periods regular. And it helped a lot.

When I was around 24 I decided to put an IUD (Skyla) and kept it for 2.5 years. When I had the IUD my periods were not that regular, but even if I missed a period I’d still have all of the pms symptoms. So, Aug/18 I decided to remove the IUD to start ttc. The first two months I got my period right on time and everything was normal, but in December my period didn’t come, I have absolutely no symptoms, pms or pregnancy and every test I took was negative. My period is more than 20 days late and I don’t know what’s going on. I made an appt with my doctor but it’s only on Jan 9th. Does anyone have any idea what could be going on?