Tommy,
Sorry to read about your loss. Been there, it's very painful and you'll start to doubt alot of things. My wife and I lost 3 in a row and almost gave up. (Minor surgery corrected the problem for her) Give it some time and jump back on the saddle when you n' the wife are ready. Please talk with your wife about it, it will be painful and hopeful at the same time. And as ThunderDan said, there is a reason why, you just may never find out what it is. (alot of prayer helps too)
The cure for me was when my son was born 5 years later!! (hopefully yours as well but much!!! sooner)
Hang in there!! (I know, easier said then done)