I was so happy to get your posts. Yes, our step-family situation adds a lot of extra stress and affects the dynamics but only people in our situation can understand. For sure, having 2 children already has made my DH much less excited and driven to have another, which has made me sad. I think he'd be perfectly happy to leave things as they are (but I'm not so happy with my seriously compromised lifestyle and no baby of my own). We have also had many discussions/arguments about whether to have just 1 or 2 of our own - with him strongly favouring just one. Sigh.
Sorry to unload all my details, but it is so nice to know that someone has been there and that everything will work out in the end if i just hang in there.