Stopped taking the pill and haven’t gotten my period

I have been taking birth control for almost 4 years now and last month I missed my period so my doctor recommended I stop the pill incase of pregnancy. I also wanted to get an IUD which is scheduled for next month so that’s another reason I stopped my pill. I’m not trying to get pregnant but I was having unprotected sex using just the “pull out method” (stupid i know)

Anyway, it’s now been over a month since I missed my period and stopped taking the pill... does anyone have any ideas as to why I haven’t gotten my period yet??

FYI: I’ve taken pregnancy tests all month and had a blood test I’m almost positive I’m not pregnant...