Dolly is right, life isn't fair-maybe fairness is something we shouldn't expect-except we are taught the virtues of it in childhood. It's really only an extension of the unfair treatment you will have suffered because of his drinking-I really see that as selfish behaviour on a par with being unfaithful. He didn't care what you thought when he was out of it, similarly he wouldn't care what you think of his dating habits. You rightly feel bitter because you, like a lot of us, have tried to put things right.
It probably won't take much to remind you why you broke it off, and it probably won't be too long before you are with someone who values you (as much as you should value yourself!).