V.W.
If you nurse him to sleep at bedtime, he has learned that THAT is what he needs to go to sleep, so when he wakes during the night, guess what he requires from you?
I agree with Missy F, except that I wouldn't start with the middle of the night wakings. I would start with his bedtime. Once he learns how to soothe himself to sleep at bedtime (which ought to be around 7 pm?), then he will know what to do when he wakes at 2:00 a.m. The only thing that will be required then, is for you to give him a chance to learn that he uses the same tools/techniques then as he does at bedtime. That means not going in to him the second he makes any noise or fusses. You'll have to give him a chance to try it on his own.
Start with bedtime first. Then, when he learns to go to sleep without being nursed to sleep, rocked to sleep, given a bottle in the bed, or other interventions by you, you can move on to middle of the night waking and going back to sleep. It doesn't mean you just stick him in bed. You should have a nice bedtime routine in place already... maybe a bottle or small snack, brushing teeth, pj's, a story (while rocking in a rocking chair?), prayers, lights out, hugs and kisses goodnight, then YOU leave. When you can do that, then he won't need YOU to fall back asleep at 3:00 a.m.
:)