My 18 day old little boy will sleep 5-7 hours at night and I let him sleep though that but should I be waking him up if he naps more than 3 hours during the day? He can sleep for 5 hours before waking up and want to be fed. He is healthy very happy and content baby. He did lose over a pound of his birth weight in the first week but after my milk came in he gained 3 ounces in 2 days.