HTBR
You have been given some very good counsel here. I attach some information on emotional affairs as your DH seems to be well and truly in one such thing:-
For many people, the emotional affair is a great source of relief and comfort during relationship difficulties. But the danger is that there is a finite amount of intimate emotional energy to go around, and when one begins to regularly invest significant amounts of their emotional energy in someone outside the primary committed relationship, the primary relationship can be seriously compromised.
Frequently, an emotional affair will deepen through consistent contact through in-person discussion and/or numerous email and voice mail messages. There becomes an excitement and ease in hearing from the person. And when this type of relationship does lead to physical intimacy, it's often a little sex and a lot of talking. The sex may be intense and passionate, but it is the feeling of emotional safety and companionship that really fuels the bond at the deepest level.
This companionship can doom the primary relationship. Once the door of emotional intimacy has been opened and the bond deepens, the person having the emotional affair cannot help but compare. "It's so easy to talk to her, and so hard to talk to my spouse" is the common refrain. "My husband always complains and criticizes, but my friend is always there, always in a good mood, and always understands and listens to me." It is much easier to open up and feel safe in a superficial new friendship compared to a long-term committed relationship.
Your husband needs to answer these questions to you :
do I feel like it's easier to talk to my friend than my partner?
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does my friend seem to understand me in a deeper way than my partner?
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have I stopped confiding my deepest feelings and concerns with my partner and now turn to my friend for these needs?
He also needs to read this too:-
If you find yourself or your partner developing an emotional affair, you need to put your attention on your primary relationship as soon as possible. Get help to understand why you drifted to this other person in the first place. Begin the work of re-investing emotional energy in your primary relationship. Turning to someone else during a time of conflict or distance often is merely escaping and avoiding other issues which won't go away. And don't kid yourself: these same issues will resurface again should you develop a real relationship with your emotional affair partner. You may as well learn to deal with them now, before putting yourself and your partner through a terrible crisis.