Before you had the baby everything was fine ... you made a massive declaration about your love for HIM by leaving someone else to be with him.
Perhaps HE hasn't realised that he thinks the baby has usurped all the love and attention that you used to lavish on him.
Most people have a change in sex life after a baby :you are usually just too knackered for a start. Can you really envisage spending your life with someone who doesn't want to know what you have to say. He is being a bit of a selfish sod if you are relying on him to be your link with the outside world, and he just can't be bothered.
Also a word of caution, boys - in the main - are solution based creatures , he may think that you tell him stuff ( a problem ) and he is telling you how to fix it ( which is not what you want - you just want to work through an issue by going over it out loud again with another adult ) and if you ignore his solution he will be reluctant to continue to discuss something again as he thinks he has already told you how to remedy 'the problem!'
Find a local baby group and even if you initially don't like it - go back three or four times - as a girlfriend in the same situation can do you no end of good at a time like now. Then you don't have to include him in the 'dull stuff 'at all.
I think once you get through the first hurdles of parenthood you will be better able to make a proper impartial decision- do not rush into it!
Have a read of this web site, you can join the forum and speak to others if you feel it's appropriate for your circumstances.
http://www.pni.org.uk/
I am married ( over twenty years ) and I do have kids just incase you are wondering.Please keep us posted, and there is usually some one you can bounce ideas off, if you need to here.