Congrats man, I know exactly how you feel cause it just happened to me too.
My girl is 4+ months pregnant and I never even remotely considered putting kids on this rock.
But that doesn't mean I'm not excited
We just got back from the doctor and we found out it's going to be a boy, and a handsome one if he looks anything like his mom.
Time to get my shit together, take some responsibility and man the fuck up.
I got this book which is pretty funny:
http://www.amazon.com/Dudes-Guide-Pr.../dp/0446178195