No Such Thing
There is no such thing as an ex-Christian. If you thought you were a christian, and now you believe you are an ex-christian, you have missed the doctrine of Christianity. All you are is simply one who thought he was a Christian but now simply is still not a Christina. Being a Christian is not based on anything you do or don't do, not on who you are or were. In other words, you don't become a Christian by doing good deeds. There are probably many pastors/missionaries/teachers/etc who are going to Hell. God promises that He will be faithful to complete what He started. Read the Bible. You give yourself so much credit by claiming that you can become something on your own freewill or deny something that is sovereignly given to a person.
Jason