Did you have a small belly when preganant and was your child weighing right on track
With all of my pregnancies my belly measures small and looked smaller then other women. My babies always measured right on track or even a little bigger. At birth my babies, all born premature, weighed on the heavier size of babies their gestational age.
Some women will carry their baby more out then other women. Your doctor will keep track of your size and the size of your baby and alert you to any concerns.