My baby never slept as much as much as other newborns.....she would take short naps and woke up often to eat. She was obviously overtired (we also had colic issue though and silent reflux). If you baby does not seem overtired and extra grumpy because of it then your LO is just fine! I read many books and came to the conclusion that, even though there are 'averages' for most babies, every baby is different!