Sometimes your kitten is craving warmth and you are warm. I would try putting a heating pad set to low, or even a heated blanket in his bed. Make sure you check it often to prevent injury to your cat. I don't know if it will change his behavior, but he might want to stay in his bed longer with the heat. Also, having a kitten means there are many things you will have to get used to and sleeping with you is one behavior that is sometimes difficult. Closing your door is one way, but get ready for a few nights of him loudly meowing and beating on the door. Putting a small automatic sprayer in front of the door will give him the message that he is not to enter there. These things can usually be found at pet stores or online.