waking up baby to eat?

My son is almost 3 weeks old. He weighed 5lbs 12oz. As of yesterday he weighed 6lbs 1oz. His pediatrician said he is gaining weight just fine. He can go hours through the night without eating but I still wake him up after 3 to eat. I am giving him breast milk through a bottle. Should I still be waking him up to eat or should I let him sleep? We don't see the pediatrician again till next week.