Sounds like Braxton hicks. The muscles at my pelvic area sometimes will tighten and it feels like period cramps. Mine is also on and off, no pattern to to the timing but it's worse when I'm dehydrated. I also noticed it's harder for me to pass motion. Gynae said the cramps are likely Braxton hicks. Keep monitoring and bring it up at your next consultation :)
Is it braxton hicks?
Jolynn Mun