Lucky1979, I could have written your post hun.
My DD is 8 months old and DH has said that there is no way that he will ever have another child. He is only 33 (I am 35).
Now, in fairness, he was never keen on having any children, so I'm lucky that I've got my DD (who is my world by the way ) and after a traumatic birth with her, I never thought I'd want another one. But now, like you, the thought of never having another baby makes me desperately sad.
In our case, I think it may be because of the massive change it's made to our lives. DH and I have had some real problems recently because I have taken to motherhood easily and as much as he loves our DD, I think he resents her slightly for the changes it's made to our lives.
DH has even said that he is getting the snip! I have persuaded him not to, just in case he changes his mind. He has said that he won't change his mind but has agreed to put it off for now.
Having said all this, I'm from a family of 5 and love having brother and sisters. But I am also not adverse to "only children" and said to DH that we have to ensure that we make the effort to let our DD mix with other children as much as possible and when we have holidays etc, to ensure that we take one of her cousins (I have a DNep who is only 5 weeks older...) or as she gets a bit older, a close friend, with us. My Mum was an only child and said that holidays were the worst times as she was so lonely.
Anyway, after all this waffle, please bear in mind that it's early days and he may be feeling this way because of the disruption to your lives, it happens. He may feel differently in 6 months or a year.
xxxx