Hello Carly and welcome.
The best way to address the "elephant in the room" is to confront it head on.
Since you've been married for some time,hopefully he'll be responsive to your approach.
Try not to offend,as this could make a bad situation worse.
You stated a previous addiction,so please try to understand things from both your experience and what you've learned in classes.
Addiction is addiction but alcoholism and drug addiction have their similarities and differences.
Protecting the children should be paramount,as they tend to pick up on the most subtle of cues.
If he's in denial,that's one thing but if he's willing to admit to his addiction,then work with him.
After all,everybody needs somebody,sometimes.