are you in your 20's? at some time in the next few years your girlfriend may change her mind.
I recommend it, it makes your life chaotic and costs money, but its the best thing in the world, you'll never be the same. Think about how you'd be in your 50's or later with no kids, I don't know anyone that said they're glad they didn't have kids, but I do know a few that are sad they didn't. Just a random internet guys opinion.