How Much Does Your Newborn Actually Sleep?

I'm wondering if it's just me who finds their newborn never sleeps this supposed "normal" 18 hours a day? He's almost 2 months now and I've never seen him sleep more than just over 15 in one day. He averages between 10 and 13. The doctor said since he's gaining weight just fine and isn't being overly fussy it's not too concerning and to let him sleep past 4 hour stretches if he's sleeping past a feeding. Even so, he's still not making it to an average of even 14 a night, and I've been told "normal" is between 14 and 18. I just can't see how that is possible. An average feeding takes him an hour or two with a diaper change or two as well as setting up and then getting him back down. When you add that up -roughly 8-10 feeds a day- to playtime and baths as well as other changing throughout the day, where is there still time for 18 hours of sleep?