Buckle in Cautious....it will be a long ride. You are in good company. Post more of your situation, please: how long you were married, how long you courted before getting married, how did he end up talking to the HS girlfriend again, how many kids, were either of you previously married, what problems were there in the marriage before he left....
The more details, the better it helps us help you.
And hang in there, and read lots and lots of other people's posts. There are other gems of information in them.