Affairs, emotional or otherwise, are quite common in almost every culture. Monogamy is a creation of human imagination, not an inborn behavior. Evolutionarily speaking, our survival once depended on promiscuity, and most humans still have that urge to one extent or another. As such, the marital commitment is one that requires resisting one’s nature. While ADHD might make it more difficult to stick to such commitments, it is hard for most everybody.
Whether true or not, I doubt your wife is interested in anything that sounds like an excuse to get out of your commitments. In other words, when you suggest your ADHD was a contributing factor, all she hears is, “I’m not sorry, and I’m going to do it again.”
If you’re really unable to stick with the commitment due to your ADHD, you shouldn’t continue to agree to it. It’s not fair to put someone through a lie.