You guys are obviously doing something right to have been together for 17 years. That's a long time to be together and not be on the same page about having kids. I went through this in my last relationship (12 years) and after much heartache I decided I would rather have him than have kids. I didn't want to end up in a situation where he resented his life and I essentially ended up raising a kid who felt unloved by one parent. It's so hard, but if you've already said no he's the one who's going to have to decide which one he feels like he can't live without, you or a baby.