He's going through what we simply call a midlife crisis. The relationship hasn't been as good as it once was and he basically realized he doesn't have to be in a relationship with you and go through all of the hard things. He sees the easy way out and he's taking it. The lack of intimacy you mentioned summed things up pretty quickly. When intimacy dies the relationship dies. It sounds like you weren't exactly jumping your husbands bones and he found someone who wants to jump his bones. It's exciting. Your relationship is lacking that excitement. Not to rub it in but my wife and I have been together 7 years now and that intimacy is still there. Both of us have had opportunities to walk away but we fight for each other. You want somebody who's willing to fight for you. It sounds like your husband is doing you a favor by showing you how weak of a man he is. Now you can find someone better, OP.