puppy not napping!

[Caroline]

My 12 week old giant schnauzer pup doesn't seem to want to go in his cage to nap of his own free will. The first couple of days I had him he went in for a lie-down of his own accord, but since then he only voluntarily goes in there to eat/drink, as I've put his food/water in there. When I need to work (I work at home) or go out I have to pick him up and put him in, no amount of coaxing works, except when I chuck some food in a kong in for him which I don't want to do everytime. I don't see him sleeping very often at all, and even when I come down in the night to take him out into the garden he's awake. I've tried creeping silently down the stairs, but still can't catch him asleep! He's exhibiting a lot of dominant behaviours which I'm trying my best with, but I've only had him 4 weeks so far. I've read in many places that puppies nap a lot, should I be concerned that he doesn't?