33 weeks pregnant, but measuring small?

So at 31 weeks I was measuring a week behind, doctor ordered a sono which showed that the baby was measuring fine, but my amniotic fluid level was on the low end, they told me to drink more water, went back yesterday and my fundal height is the same, doctor didn't seem concerned so I wasn't either, until later, now I'm worried I'm measuring small because of the amniotic fluid. I will be calling the doctor, but just wanted to see if anybody else measured small with a lower end amniotic fluid level,