Its really important to address your fears. Why are you afraid to leave him alone if he's upset? Is he safe? Have his needs been met?
So many of us cannot listen to a crying child. My husband immediately retreats to the basement or puts the crying baby in a room and closes the door. However, sometimes kids cry, but they do stop eventually. Parents who give in because a child is crying have BIG TROUBLE on their hands as the kid gets older. They know exactly what to do to get their way.
Obviously the idea is not to just let him scream until he stops hours later of exhaustion, but to teach them to soothe themselves. Is the crib safe? No climbing out. What about the room, is it nice and DARK? Lights can be distracting to light sleepers. What about white noise? My family has used fans to drown out the neighborhood noises at bedtime. It also helps if we need to get up early or in the middle of the night, or with staggered bedtimes for the girls who share a room.
I would suggest letting him learn to cry it out. He's not an infant that can't communicate any other way. DON'T lay down with him. This is a bad habit and teaches him to NEED you to fall asleep. Have some cuddle time after the basic bedtime routine you do, maybe rocking in the rocking chair singing some quiet lullabies and then lay him in bed and let him know its time to sleep. He will immediately sit up and start to cry, lay him back down and say that its time to sleep, and then walk out of the room. Stay close to the door, or watch your monitor. Give him 5-10 minuets to settle himself. Then go in and give him a hug, tell him you love him, that its time to sleep, and lay him down again and go out. Next time you go in, don't talk to him, just lay him down and go out. Keep doing this and give it a little bit more time between going into the room. He's going to learn that he can't get out of his crib and you aren't going to give in.
Don't let his crying bother you, he knows it worked before, you have to teach him it won't work now. Prepare for this taking several hours, and it might be a week before he's learned it, but above all else DO NOT give in. If you do its all over! They have to learn by consistency, if you give in once, they'll always wonder if you'll do it again, and chances are you will. That is very confusing to a kid. Also it sounds like he's been sleeping with you before, so remember this is all new to him, so he's loosing some of the security he had before, that's why he's waking up every time he moves - you're not there to bump into. However, he'll get it, it will just take time.
Good luck, I know this is tough, but you BOTH need it! Mom and Dad need sleep and privacy!!! ;)