Uterus keeps getting hard?

Cam • My sweet little pea is here! Born June 1, 2016 🎀
25 weeks tomorrow and I keep getting tightening in my uterus. It gets rock hard for about 30 seconds and then goes away. It's been a good 3 days since then. They come and go randomly. Painless, but you feel pressure in the stomach area. Is it BH? Ftm so I have no idea, Google is giving me different answers.