dizziness at 31w6d

im 31w6d and have been getting kind of dizzy and lightheaded. I brought it up at my last appointment and the doctor said it's probably either low sugar or low blood pressure, but I don't know....honestly, I have a hard time drinking enough water and I know I don't drink nearly enough so maybe it's that? I really don't know. should I maybe call the doctor? I feel kind of dumb calling.....