1 day late

I was suppose to start my period yesterday. I started having cramps 2 days ago and thought I was about to start my period. I still have cramps on and off but still no period. We use the withdrawal method which I know isn’t 100% effective. I did take a test today and it was negative.

Wondering if anyone experience period like cramps around the time they were suppose to get their period but ended up being pregnant....