I think that you've got to find another outlet for your feelings. Have you tried volunteering in the baby room at your church, or offerring to babysit your friends' babies? You could also channel your desire for another baby by volunteering to hold babies in the hospital that need to be held and loved, but don't have enough nurses or parents to go around.
I was having the same kinds of feelings you're having with respect to adopting another child. We have two bio daughters, and one adopted from China. I would REALLY like to be able to adopt another child from China, but my husband has said no. And because of our age, I think he's probably right. But that doesn't make the want go away. So I decided to start and lead, along with others at our church an orphan care ministry. I've been able to fulfill the desire to help children in need without adopting ourselves.
I will say, though, that if God made it clear that He wanted us to adopt again and my husband was on board, I'd jump at it! It's been a blessing for our family!!!!
Hope this helps a little bit.
M.