Braxton or baby?

Ra
I'm either having Braxton Hicks or the baby is pushing against my belly with all his might. At 20 weeks I don't know if he is big enough to do to this. It takes my breathe away and wakes me up at night. My belly will be super hard, but just in the middle. Water seems to help. Nothing worrysome, just don't think I had BH till around 25 weeks with my first.