I have long wanted to have an affair...

I have long wanted to have an affair with someone, but 1 particular person at church. For 3 years I have been so sexually attracted to her, but I haven't acted on these thoughts. I've stopped masturbating and thinking of her, because it's not real. As I've realized that the fantacy will never happen, I've grown depressed about my marriage. My wife deserves better, and I doubt my salvation. While I'm active in my church, this means little to nothing. Plenty of lost people attend church, who are destined for hell. Now that I'm 40, I realize that I may be one of these too. While I believe in the gospel of grace, I haven't seen any huge change in my life. I only have the hope in the cross, and that I grieve over my sin. What a pathetic man I have become. While I'm not suicidal, I am totally embarrassed about my sin. If my Mom, wife, and kids knew what I have thought and did with my body, I could no longer face them. That being said I still greatly desire to have her...the one that I can't have. And yes..if I knew she felt the same towards me, I would have sex with her without any problems. I am afraid of the second death that I will face.