Girls, how do you figure out how your baby is positioned in your belly…

Girls, how do you figure out how your baby is positioned in your belly? I can't feel where the head is, where the butt is, etc., and every pregnant woman you look at seems to know like an X-ray where and how their baby is lying. The kicks in my belly are mostly around the navel, they're strong and my belly shakes, but sometimes I feel pressure in my bladder — how do you tell if it's legs kicking or arms?