Cramps after orgasm???

Tricia • Hi y`all!! I`m 28 from Alabama! I`ve been married 11 years to my best friend. We have a little boy who just turned 10 and we`re trying for a rainbow baby
I've NEVER done this before I'm kinda freaked out. Ok so hubby and I make love and when I went to the washroom to freshen up I had cramps in the center very low part of my tummy. It lasted about 10 min coming and going about 4 or 5 times in all. It wasn't too painful just caught me off guard. What could this be?