Hi, there,
I had my son with me in the bed from age 2 until 3.5 years old. My second baby was born when my first was 3 years, 3 months, so for three more months, we were in a very crowded bed! Needless to say, at about 3.5, my older son felt too squished in the bed, I think. He was smashed right up against the wall, so he started to want to go back to his bed for the first time in 18 months! Of course, after the first night, he had second thoughts and wanted to come back to our bed, so this is how we handled it: we had nice, soothing music that he got to play in his room (which he really loved) and we gave him a night light that changes colors, so he can watch it and it lulls him to sleep. For about the first month, he would come back to our room in the middle of the night, but then it became less and less. Soon, if he woke up in the middle of the night, he would ask me to come to his room for a few minutes (less than five minutes) and I would. He was fine when I left. Finally, he figured out that he could just turn the music on by himself, so instead of coming into our room anymore, he just turns on the music in the middle of the night. I hear it come on once or twice a night, though it is also become less and less frequent. Maybe you can try the night light and music combo to help your son. I usually stay in the room for about 5 minutes before he goes to sleep and then I give a kiss and he is fine with me leaving before he falls asleep. Now if only I can get my 8 month old to sleep on his own!!! Good luck!