Heather-
Looking in from the outside its easy for us to say, but this isn't about you being inadequate in any way, but about him sinking to a level in which he feels comfortable. He probably wishes he could be good enough for you, but until he can get his disease controlled he can't be, so it's easy to move to a place where expectations are low and he can drink and act however he wants.
Give yourself and your babies all the love that he's not capable of giving! Prayers going out for you and your family.