My stomach is shaped like a childs.?

I am 20 years old and my stomach looks like a childs stomach. I'm 5'3 & 120lbs so i'm not fat. It reminds me of how little kids have bulging bellys. I don't remember why they have it but my stomach looks like it after i've eaten after a while. If i'm starving, my tummy looks thin and toned but during the regular day its child like. Any ideas why? Maybe it is just from eating but its so different compared to other peoples.