Just a quick disclaimer: I don't believe in the existence of the "dry drunk." As far as I know, sobriety is sobriety.
Anyway, my wife felt similarly when I stopped drinking. The thing is, when a person drinks, his personality can change dramatically. When I drank heavily I enjoyed different things, was interested in different things, etc., compared to when I'm living sober. So when I stopped drinking, all those interests and favorite activities changed back. This caught my wife off guard, and we had to find new things in common to enjoy. But before that happened, we went through a period where it was tough to find fun things to do together. For a while we basically lived separate lives.
If your husband is anything like me, then perhaps he is going through something similar. In other words, it could be that his tastes and interests have changed, and that you guys will have to find some new things in common, just like my wife and I had to do.
Of course, it could be something else entirely. But that's one possibility. Good luck figuring it out.