DEAR AMY: My wife and I have been married for 10 years. We have two children and between the kids and our jobs, we are super-busy, but we are making things work. Recently we had a very rare date night together. We both had a little bit too much to drink, I guess, and we were having the kind of intimate conversation we haven’t had in a long time. I can’t even remember how this came up, but my wife admitted to me that right after we became engaged, she had a brief fling (that’s how she described it) with her ex. She described it as a “last fling before I got married” sort of thing. I was complet…