J.W.
I highly recommend the book "On Becoming Baby Wise". It was written in the '80's but it is still very relevant today. It basically talks about how to put your baby on a feeding and eating schedule during the day, so that they get enough nutrition and you don't have to wake them at night. My son was sleeping through the night (7-8 hours) at 8 weeks old. Since he was gaining weight appropriately, we were not concerned about waking him to feed him. As long as your baby is gaining weight and growing like they should be, I would NOT wake them at night, no matter what my doctor said. Good luck!