D.H.
First thing, you have to be consistent. He needs to know that if he cries, it doesn't matter. Stand your ground. Now, with that said, you have to make his room, a good place. Do you have a rocking chair where you can nurse him in there? Stop nursing him in your bed. You might try putting him in his crib, and reading to him at night. Even just sitting in the room with him. Try putting glow in the dark things on his walls to look at.....or on the ceiling. If you stand your ground, pretty soon he will realize it's time to go to bed. And you've only just begun, wait till he gets into a toddler bed!