Why my stomach isn't blowing up?

This is my first pregnancy and im 17 and im 3 months and 3 weeks ill be 4 months dis saturday.When do i i start blowing up i barley take my vitimans because they make me sick sometimes but now im startin bak too take them again.. neways i got a bump but when i take pics of my self look like im big but when i look down at myself i see a bump but if you look at me you cant tell im pregnant unless if you look from the side.