When I got Juju 6 yrs. ago, we went thru this. She was very small and just didn't seem to remember to eat. I fed her human baby food, chicken, off my finger every 4 hrs. or so, also mixed in some soft puppy food. Keep her stress low and pay particular attention esp. after play, as that can make the sugar bottom out. I also kept food in her crate at all times, day and nite. Very small pups are a lot like human newborns they don't know what is wrong when they are hungry and have to be fed on a schedule. IMO. Good luck with your baby.