I'm sorry you're going through this. It must be completely devastating.

I have a couple questions, though. First, how old are each of you? And where do you see this relationship going? Have you two had a recent discussion about your futures? Do you have plans to get married? If so, what's holding you back now? If you don't have plans to get married, is that because neither of you actually want to get married (which is fine), or is it just that you haven't actually talked about marriage?

The reason I'm asking these questions is because i"m trying to get inside her head a little. Six years is a long time (I was with my husband about 6 years before we got married), and I"m just sort of wondering... Is she getting bored? Restless? Is it that she's worried your relationship isn't going anywhere? Was she crying out for attention, to feel like you REALLY love her, and aren't just used to her and comfortable with her? Something must have happened that pushed her over the edge. I'm not trying to put the blame on you at all, not in any way. I'm also not trying to justify her actions. She made the decision to stray and that was wrong. But I think you two need to have a serious discussion about what you both want out of the future, because if it's not the same thing, you won't be able to move past this. Try to have the conversation in a calm manner, so neither one of you ends up on the defense, because that just halt all productive communication from happening.

Good luck