I wouldn't really take any of it to heart. I know that's hard to do but that's what I've realized. The same thing has happened to me, which has made me hesitant to start any threads myself. (I tend to mostly reply to things now.) You can't help but feel personally responsible for lack of interest in something you post, I know. But like everyone else has said that can easily be attributed to the vast amount of posts that happen! You go away for a little while and there's no hope of catching back up! That and you are right, there are groups of friends, and of course you're going to want to post and talk with your friends more!
Your baby is just precious! Don't feel bad, it happens to everyone! Maybe we should make our own group of friends. You know, the people that feel left out.

Then we could all reply to each other.