You poor thing, I really feel for you. This wasn't entirely your fault because your husband knew you weren't on birth control. It's a mystery why he didn't use a condom or the withdrawal method if he really didn't want another child.

Yes, you should have talked about it more before it happened but it's already happened and it's no use dwelling on the past.
My husband's ex wife did the same thing, she just stopped taking birth control because she wanted a baby but my husband wanted to wait a little while because they were only just married after having been together for only 9 months...... BUT my husband never used protection, this is what stumps me, if he was so angry about her falling pregnant why then didn't he use a condom or the withdrawal method (like he did with me at first)? He loves his son very much and obviously doesn't blame him but still holds a grudge against his ex-wife for forcing it upon him.
Maybe your husband thought it would take a lot longer to fall pregnant or maybe given your age he thought it wouldn't happen?
I know you must be over the moon to have fallen pregnant so just concentrate on the baby right now. Good luck with everything.