brax hicks after orgasm

Katie
I'm 21 weeks so these Braxton Hicks contractions don't hurt, but there is s definite "wrapping around" feeling and a hardening of my belly... Only happens after orgasm (so far). 
Does anyone else have this? 
Is it totally safe for baby? 
I don't think my midwife believed this is what I'm having, since it's so early, but I swear it is! 
I'm a FTM so wondering What do B.H.s feel like to you?