Braxton Hicks or Preterm Labor?

Alexa • Expecting a baby boy! 💙💙💙 09/09/2015 Aiden Michael Esquivel FTM
My stomach keeps tightening up all around my bellybutton area it doesn't hurt but it feels uncomfortable. It feels like if the baby were to press his butt up against my belly button but more consistent. It is happening like every couple min but only for like 20 sec. Any idea?