Contractions or strong movement?

Amy • My first pregnancy!

Every now and then my stomach will jolt out to the side. It feels like a lot of pressure and it's stays like that for like 20 seconds before slowly going back to normal. Sometimes it makes me gasp because it's unexpected.

I've just been thinking it's the baby locking her legs out or pushing out. Could it be braxton hicks? I'm a ftm and will be 36 weeks on Monday.