You are discovering that the old myth of "get them good and tired so they'll sleep all night" is just that - a myth. Over tired babies and preschoolers actually have a harder time going to sleep and a harder time staying asleep.
Watch him like a hawk and pop him into bed at the first sign he is tired. Rubbing his eyes and yawning are too late. You need to find that magic few moments when he is first showing he is tired.
Try to reestablish a schedule. He may be dropping to two naps or he may still need three. You'll have to figure that one out and then stick with it.
Get him into sunlight within an hour of the time you want him to wake up in the morning. This will help to reset his internal clock.
at 10:03 PM on Jan. 6, 2009