HI -- been there, done that. My suggestions:If you are set on continuing to co-sleep (and I did with both my little ones)get yourself a co-sleeper. It is a crib that attaches to the bed. With it there, you have the baby close but don't need to worry about rolling over or having the baby roll off the bed.
Next:Get yourself a full body massage and, if you belong to a gym, start swimming. I know how it is to be exhausted but there is a curious thing about sleep, the tireder you are, the harder it is to sleep. Swimming is an excellent exercise for relaxing.
I am assuming that you don't drink caffeine? If you do, don't. Both Camomile and Mint teas are good for relaxing bodies, but don't make them too strong.
Finally, train yourself and your son to go to sleep at exactly the same time. Lie down, make sure that the room is truly dark -- research indicates two things (1)Light stimulates the pineal gland and keeps sleep lighter and (2)especially in older women, light during night time sleep may be implicated in the development of breast cancer. So, a DARK room. Then lie down, baby in co-sleeper, and put on some quiet music.Your son may complain a bit. Rub his back and then leave him be. The truth is, he does need to learn to settle himself back to sleep -- and so do you. Trust me, I KNOW how hard that is but for everyone's health and sanity, you need to help him learn. If you haven't read E. Pantley's 'No cry sleep solution', find it and read it. She is a very gentle teacher.
Finally, we discovered that there are certain foods, bananas and turkey top the list, that have natural trytophane. My sons both eat a banana before bed. It gives their tummies something to nosh on, they get lots of potassium for their muscles and the tryptophane is a good addition to their rest.
Jenny
PS One other thought: Some kids, like my eldest, are extremely sensitive to environment. Check that your son is neither too hot nor too cold, that his bedding isn't causing an itching (Detergents can), that there is no stray light or sound that might bother him. Amazing what children can detect.
Best wishes.