I just had too smile though it's a serious issue....wanking while praying is kind of perverted too isn't:-).... I can't see anything wrong in havin fantasies when your with your wife....Is a well known fact that many men do. hetero or not. And a whole lot of women too. WHo knows maybe your'e wife is thinking about jhonny Depp or someone else when she's with you.
And finally fantasies as long as they stay in you're head no one is hurt....perhaps only your self....