my gs puppy

Question
got my gs male puppy just over a week ago...took to vet yesterday and he weighs 6 1/2 pounds...she seemed concerned..asked about feeding etc. he is eating purina puppy one  but only eating about 2 cups a day ..he eats when hungry...has energy...drinks water..plays but he just doesnt seem to eat enough...i looked at weight charts and thought omg hes way underweight.  what do you think? oh and tomorrow i am taking back to vet a fecal test and she is reworming tho kennel did this.  she says at his age he should sleep from 11pm till morning 6am and since he is getting us up to go to bathroom there may be a problem.. I thought we had a great puppy and now am scared.

Answer
I wish you gave me the age.  He must still be fairly young.  Manypuppies don't make it over night until they are past 2 months.  

German Shepherds tend to be light eaters.  2 cups may be enough for a younger one.  As long as his ribs don't show too much, I wouldn't worry about it.