I'm 30 weeks pregnant and everyone thinks i'm 3 or 4 months pregnant! i eat and drink plenty of water! is it normal for me to be so small?

Doesn't sound right: The baby bump does not show before about 20 weeks, which is about 5 months, so your family and friends assuming you are 3 or 4 months does not sound right. While you still may measure small, i.e., the height taken from the top of the uterus to the pubic bone may be less than 30 cm, it is the increase in fundal height in between prenatal visits that is important. I should increase by 1 cm per week.