I reread my original post, and I hope that didn't sound too insensitive. But seriously, what I was trying to get across is that when you have a child, the whole world revolves around that child, no matter how intelligent you are. Like women who get married I guess, the whole world revolves around their wedding... not all women are like this, but for a lot of women, it's easy to get caught up in their own little world.
And that it's normal for relationships to change. It doesn't mean you don't like each other anymore, it just means that you don't have a whole lot in common atm. Maybe you will in the future, maybe not.
Just be honest and explain your feelings. She probably will have no idea you've been hurting.