Braxton hicks?

Ok sorry if this is tmi... DH and I had sex tonight (1st time in a while). For about 3 or 4 minutes afterward, my uterus was super hard and tight and I could feel the shape of it with my hands. No pain. I never had BH contacting with my first, is that what it was?

I am 16 weeks 6 days if that makes a difference.