I was thinking about your post about being hormonal...I really believe that codependency, especially in women, is partly the nurturing instinct gone awry. As advanced alcoholism worsens, the drinker becomes more and more child-like in affect and in actions. They even lie the way little kids do...badly. And then there's the clinging to a bottle...
My theory is that as nurturers, we see that inner child in distress and slowly lower all expectations of them to behave as what they are...adults with a big problem only they can address. We take on more and more...I didn't live with my ex, thank goodness, but I see so many threads here where the one adult is basically a single parent caring for another "child," in the alcoholic, while that alcoholic does less and less in terms of adult responsibilities.
Your pregnancy is preparing you for nurturing your new baby, so you have even more of an urge to nurture right now. So maybe recognizing that might help you avoid taking on your third "child" to parent, in your husband?
Sending you a hug.