Andy,
My wife had a miscarriage the first time we tried to have a baby. Unfortunately I think its quite common now for women.
We waited for 3 years before trying again....the result? the cutiest baby boy you ever did see.
I know its hard on her and you right now but time does mend old wounds. You sound like such a great Dad (and a wonderful son), let her know that there are other women/couples out there that have had the same experience and have come through it.
I have to believe that you have so much good Karma stored up for you Andy...sooner or later you are going to see some of it. You deserve it.