Small Belly ? 31 Weeks?

Lydia • 19yo Momma of a handsome baby boy (surprise gender, waited till birth) 10 hour labor 💙 Born 09/06/17 7lbs 1oz 19 1/2 inches 12:44am Breast-Feeding Cloth Diapering Baby Wrapping
I feel like my belly is small for 31 weeks... is this normal size?! Doctor says I'm measuring good. But I feel like everyone I know at this week is bigger than me.
Maybe I'm being dramatic and need to stop worrying... #FirstTimeMom!