Some of the replies on here have been brutal!
OP - I was in a somewhat similar situation a couple of years ago. My husband was addicted to drugs. I didn't know about it for around 12 months. He was buying them online, with my bank card.
I found out. He downplayed it. Said it wasn't a problem. It definitely WAS a problem. He didn't sleep EVER, didn't eat, and looked like death.
He was suicidal - and blamed me.
To cut a long story short, it all came to a head and I made him move out, leaving me and our 4 children.
Then, and only then, did he realise what a mess he had got himself into, and there was nobody else there to blame but himself. He told me he was going to kill himself, almost every day. He didn't.
He kicked the habit, on his own. Me and the kids had no involvement in his life while he did that.
Several months past, he was clean and happy, and we got back together.
It obviously wasn't as easy as it sounds, our life was hell and I still haven't quite forgiven him, but my point is, sometimes a bit of tough love is the only way, and you don't really know how anybody will react to an ultimatum, until you give it to them.
You need to be selfish, and concern yourself with your own sanity (and your DC's), and stop worrying SO much about your husbands.
It's hard, I know. But now might be the time to give him an ultimatum, a time frame, and warn him what will happen if he doesn't sort himself out. Losing his job might just be one of the better consequences to his habit, compared to losing his wife, children.....or life!
I'm here if you want to ask any questions. Look after yourself.
It doesn't always have to end up with the worst case scenario, and I'm here to prove that.