I think that your wife having an EMR of her own is a good possibility that you should explore. How would you feel if that were true?
This is a good question. Although it's impossible to predict what my true feelings would be in that situation, I am going to say that I would actually feel a sense of relief.
At the beginning of Chapter 9 of Passionate Marriage, Schnarch recalls a session with a young married couple, Stan and Florence. One of their conflicts centered on Stan's admission that he thought of other women during sex. Florence responded with indignation. Stan countered that everyone does it. He accused Florence of doing it. At first she denies it, and then backpedals a bit. Stan gets really angry about this.
Schnarch cools Stan down by asking him, "If you believed what you said when you insisted that Florence thought about other partners too, why are you so upset when she finally agrees with you." (Schnarch, p. 241) Stan replies saying, "I guess I wanted to believe her denials. I knew she must do it, but hearing it confirmed makes me feel insecure." (Schnarch, p. 242)
Schnarch then goes on to say that we may state our desires for fidelity in terms of the commandment about not coveting a neighbor's spouse. In reality, we're usually thinking in terms of idolatry. Our spouses are supposed to "worship" only us.
Although Schnarch was talking about where our minds are during sex when he wrote about that, his question to Stan generalizes well. Having struggled with the longings myself and having read about other's struggles, I can empathize readily. There is no room for indignation if I were to learn that my wife was having an EMR.
Simply put, I'm at a point where my desire for truth outweighs my narcissism.