If he wants to sleep, let him. He will determine when he’s sleepy and he’s only 3 weeks old, so he is still sleeping quite a bit. He is old enough now to be able to control his own body temperature, but having warm fleecy blankets in his nest is a must, even something he can crawl under and stay warm. When kittens have littermates, they lay in a pile, keeping each other warm.
He might be old enough to start litter training, it actually depends on the kitten. After eating, place him in the litter tray and take his paw and scratch the litter. If you have some poops put them in there and see if this triggers him. Also you can pee him over the litter to put his scent in there. He will eventually get the hang of it. Make sure you have nonclumping, unscented, clay litter for now. They have to be able to smell their own scent and strong smelling litter turns cats off enough that they don’t even want to use the tray. Make sure you have a tray that is low enough for him to get in and out of easily on his own too.
You can put about 1/2 teaspoon of pate style wet food in the formula bottle, and open up the nipple. I actually cut the tip off and shake it very good and feed it that way. They get the extra nutrition which keeps them satisfied longer. You can keep offering a tiny bit of wet food on your finger on the roof of his mouth, or on a spoon and eventually he will be interested in it.
Check these links out too they will be helpful to you.
Bottle Babies
http://messybeast.com/handrear.htm
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