He may actually think he needs it for his job, but that is an illusion. Most A's will eventually lose the very job they think they are using for.
A's will keep using, even when it's not pleasurable any more, because that's what we do. I would smoke crack, get numb for a while, then feel horrible about what I had done, and smoke more to forget the bad feelings.
Badgering him to get help is not going to work if he doesn't WANT to get help. If he does it, just to please you, it won't last and he will have a major resentment toward you...and you will have one toward him.
My biggest concern is he is using, in the same house as your kids. You are putting yourself, and your kids, at a huge risk.
The first thing I would do is tell him he is not to use in the house, or around your kids, and be prepared for what your consequences to him will be if he does.
Try to keep your focus on you and the kids, and what you will, and won't, tolerate. If he isn't intersted in stopping, it's going to get a lot worse.
Hugs and prayers!
Amy