HI T.,
I feel for you....all mom's do! I have my own bias, which you'll see below. While you may want to consider seeking advice from specialists, I would also strongly encourage you to consider co-sleeping with him for a while. We have 2 boys, ages 3 and 6, and they both still sleep with us in our king size bed most nights, and have on and off since they were born. We all sleep well (except when they are sick - but that's true no matter if a child is sleeping in their own bed or not), and some nights the older one chooses to be in his own room and bed. Basically, they both know they are welcome to sleep whereever they want, in our bed or their own.
When I was first pregnant, I never intended to co-sleep with my children. But after lots of reading and research, it just made sense to me and my husband, who is very supportive of our family bed arrangement. I would encourage you to do your own research and reading about co-sleeping. A book called "The Contiuum Concept" by Jean Liedloff would be a good place to start. Evolutionarily speaking, babies and young children aren't "wired" to sleep alone, isolated from their mother or siblings. Children do have different sleep cycles and patterns from adults, and it's important we understand that fully before we assume there is something wrong when they wake up so often. It's natural and normal. We've never let them cry it out -- which has meant less sleep for us -- but in the long run, it believe it's been well worth it.
Both our boys fall asleep well on their own, and love to sleep next to each other, but aren't dependent on it. They are well adjusted and self-confident young boys. Sure, I would love to have a little more room in my bed sometimes, but I know I am going to miss it terribly when they both move on to their own beds. Which they all eventually do. :) My husband and I both work full time, and sleeping next to them is one wonderful way we get to be with them.
It may be that you could both benefit from trying co-sleeping for a little while. He might feel more secure, and you might get more sleep! :)
Wow -- I didn't intend for this to get so longwinded. You can tell I'm a real advocate for co-sleeping. I do, however, realize every family needs to do what works best for them. Best of luck -- and remember the mama mantra of "this too shall pass".
A.