sleep problems xp

DS is having a rough time staying asleep when he used to sleep pretty good if not all night... when he wakes up, he usually hums for a minute or two and then falls back to sleep but his humming sessions seem to be getting longer and longer almost 30+ minutes... which makes me feel awful for not going in to help him... 

when I do go get him and we rock, he falls back to sleep pretty fast.... however, on these nights, I can't set him in his crib without him waking up again... since he is a belly sleeper, you have to kind of roll him in....plus my bump makes it doubly hard to set him down without waking him... which usually results in us sitting in the rocker for 2+ hours

1) would you go in if he's not crying, just humming?  

2) anything you would suggest to help him sleep? He has a sound machine that's on all night (we live on a busier road in our neighborhood), a pacifier and blanket... I have brought him to bed with me but he doesn't sleep well for long there, and I have to get him asleep before putting him in bed with me, otherwise he just stares at me and babbles and doesn't go to sleep...