3 days late with cramping!!

Hey ladies. I'm 3 days late for ms flo. I cramped all last week off and on. And still having some mild cramping. I took a pregnancy test yesterday and it was negative! 
We've been trying for 15 months for baby number 3. I took out my IUD back in February of 2015. I finally just winged my 2 1/2 year from breastfeeding 3 weeks ago. My periods are pretty regular 28d-29d. I'm never late. Early I'm a day early or I start on the day of! 
What are your thoughts ladies?