Honestly, I would play it by ear and live your life normally. Whatever he does or doesn't do really doesn't effect you anymore than you allow it to. He is responsible for caring for himself and because you're pregnant you are responsible for caring for yourself and that baby that you're growing. Put yourself in the most relaxing situation you can. Even if that means ignoring your husband. I agree with Grits that the inability to buy alcohol for a weekend does not equate to sober and where there is a will for an alcoholic to drink there is always a way.
In the meantime, what can you do for yourself? Do you have friends or family nearby that you can visit and maybe stay the night with so you can focus on taking care of yourself and maybe even have fun?