I really don't have any advice....just wanted to continue to reassure you that it isn't anything to worry about. You are doing the best thing by letting your son wear pull-ups at night. He probably sleeps too sound to be able to wake up during the night. My husband and I wore ourselves out taking our daughter to the bathroom once or twice at night. She would never know we'd done it because she would sleep so sound; but we would be exhausted from interrupted sleep. They didn't have pull-ups in those days and I refused to put a depends diaper on her. But she did out grow the problem.
Your son's bladder will grow as he learns to hold his urine longer and longer through the day, too. Then he will be able to hold more urine for longer periods of time at night. Try not to make an issue of it. Believe me, he'd go to the bathroom if he could. I don't know any child who wants to wet the bed. I was a bed wetter until I was in elementary school, too.
I wouldn't put too much thought into the emotional thing, either. He probably plays hard through the day. Is he hard to wake up in the mornings or naps if he's not ready to wake up?
Be supportive of him. By all means, don't shame him. He's more ashamed of it than you can imagine.
I've been a professional child care provider for over 20 years. I've raised two daughters (one was a bed wetter), and have 4 grandchildren (one was a bed wetter). He'll outgrow it, I'm sure. Good luck and God Bless.