An alcoholic who is not well on his way to recovery has no control whatsoever over whether or not "this happens again." If he had control over that, he would not be an alcoholic. It's probably not exactly that he is lying to you...but he certainly isn't telling you the truth either. He is probably not is a position to truly know what the truth is...and unless he has thoroughly completed Step 1 (We admitted we were powerless over alcohol, that our lives had become unmanageable.), he most certainly has not yet acknowledged the truth even to himself.
Someday he might -- but, then again, he might not.
If nothing changes, is this the kind of behavior on which you want to try to build a marriage and parenthood???????
Take care of you -- freya