I have a question.....

How does a person get a B-belly? Im considered a small "plus sized" i fit in M and L shirts and my bottoms are a 14. Im 11 weeks and 3 days and my belly is very round and looks pregnant. Im not trying to judge ornpick fun of anyone because every pregnancy is beautiful! I just wondered because a lot of skinny people tell me "oh why dont you have a stomach and a pouch" and im left in the twilight zone cuz idk what they mean.