Rob, I can imagine how it hurts you to see other families when you are with D. Try to realize that is all you see because you are sensitive to it. Maybe you should look into a group called Parents Without Partners. I know it helped a friend of mine, in fact she met her second husband there, but that is not what they are about. They deal with exactly what you are going through and give each other support. Maybe there is a group in your area. It is also great for the kids because they meet other families like theirs and do not feel so isolated
