Weight gain?

Im 30 wks now, from 50kg (1st prenatal checkup) to 59kg. Sabi ni doc maliit size ng tummy ko for the number of weeks so she advised me to have an ultrasound on April 12 para macheck size ni baby. Pero I assumed it might be dahil retroverted ang uterus ko, pbliktad pwesto ni baby instead na paforward sa tyan.