My DH is adamant that he only wants the one (he was adamant before she was born as well, though). I'm just going to bide my time and wait and see what he thinks when DD is a bit older.
And to be honest, somedays I think I don't want another baby. As much as I love my gorgeous little girl, I wonder how I'd cope with another one.
As for your DH, maybe get him involved a bit more in the parenting? Looking after DS for longer periods of time, while you go for a walk around the block etc? Or looking after him while you are in another room. Just a thought. I have heard that some Dads feel more comfortable with their kids as they get older.
As for the have another baby issue, I'd just wait it out for now.