One reason I wanted to print your letter is because I hope it will be a warning to others tempted to go down the same road you have. Sin always has consequences, and those consequences are always bad -- without exception. The Bible's warning is true: "Do not be deceived: God cannot be mocked. A man reaps what he sows" (Galatians 6:7).
Tragically, however, it's too late for you to heed this warning -- and to be frank, no matter what you do, the path ahead is going to be hard. My prayer is that you will end this illicit relationship (which has no future), and that you will take the initiative to tell your wife about it and seek her forgiveness. To do otherwise is to keep living a lie -- and the Bible warns that "The Lord detests lying lips" (Proverbs 12:22).
It won't be easy -- but if your wife finds about the affair out on her own, it probably will be even more difficult. No wonder the Bible warns that an adulterer will end up saying, "I have come to the brink of utter ruin" (Proverbs 5:14).
Most of all, open your heart and life to Jesus Christ and seek God's forgiveness for what you've done. Then ask Him to help you repair your marriage, and to rebuild your life on Christ and His will for your life. The Bible's promise is for you: "Blessed is he whose transgressions are forgiven" (Psalm 32:1).