A vet that doesn't know nothing about birthing? I'd have to get another more experienced vet.
We had our first litter of yorkies April 29th. My momma weighed 4 1/2 lbs pre-pregnancy. She got up to 7+ lbs during her pregnancy. Yes, she ate VERY well!
PM me if you have any questions. I'm not as experienced as many other breeders here, but I'll tell you all I know from my experience.