Coming off the pill and Cramping?!

Okay, here’s my backstory! I came off the pill (tri-previfem) where I had 5 day cycles every 28 days, always right on time. I always cramped the day before I started and then during my cycle and that was it! We are currently TTC and I was due to start my first period off of birth control this past tuesday! It’s is now 3 days late. I have been having awful back and stomach cramps for over a week now with no other signs of my period? Took a pregnancy test Wednesday and it was negative! Wondering if anyone else has taken this birth control and if you had similar symptoms coming off? When did your cycle go regular? When do these cramps stop?