idw, ok he's been lying, and you've been taking counselling seriously, so of course you're angry. But now he's come out and told you the truth. He doesn't want to work on the marriage, and he's been drinking secretly.
He probably took this long to own up because he was scared to be honest. It's very common. If you can bear it, go back to counselling with him and work out the best way to separate. It will be painful for you, and possibly him, but it's a controlled environment where you can express your feelings with the counsellor making sure things don't get out of hand. That should help you with moving forward.
There are many advantages to having an amicable divorce, and the biggest one is how the kids fare. You've been told he wants out, now make the best effort you can to look after your own interests, and the kids' and keep a reasonable relationship with your ex.
Sorry if this seems brutally frank. I've been through divorce which had it's rough moments, but today everybody benefits from my ex, his wife and I getting on very well together.