Start by reading THE LIST:
THE LIST (Print It) - Divorce Forum and Child Custody Forum
It will help you understand what is coming. Secondly, don't panic. Many, many people have been in the same situation you find yourself in and it has turned out OK... though it may get worse before it gets better... it will get better.
The first thing you need to do is decide if you want the marriage to continue, if it is saveable, and if you think you and your wife are willing to work on it. Divorce is NOT an attractive option but it is a possibility.