My reply will come from two different approaches.
I am curious how long you have been in this home? Did you smudge your home prior to moving in? If there is something that is frightening him for real you can aid in moving the negative energy out by smudging. Be sure to open a window to allow the negative to move on out. You can often times have your pastor bless the home as well. These two things will lighten the environment that may be heavy or frightening for him. He may not see anything, but children can feel and are more sensitive to our surroundings and the energies that may be within them.
As far as sleeping. None of my children like to sleep without me. My 36 year old husband passed away and for almost a year my 16 year old slept with myself and my two younger sons. We all shared a king size bed along with the cat. Everyone slept, everyone felt safe. Both my husband and I had always co-slept with our children and I have yet to experience anything negative from it. I strongly feel that as American's we lost some of the old ways. There once was a time when everyone in a home shared, worked together and sending our children off to their own "space"/room was not needed. Yet those days yeilded strong independent adults.
And as a follow up -- my now 18 year old willingly retreats back to her room for undistrubed sleep.
here is a link on smudging. I have smudged both my properties and when life is tough, I smudge again. It really helps as crazy as it sounds.
http://healing.about.com/cs/native/a/smudging.htm