Are there other signs of drug use? Money disappearing could be any number of things such as gambling, other women, a shopping problem, secret debt, or many other things. Drug use usually comes with all kinds of behavioral clues and personality problems, not just disappearing money.
My ex husband married me without telling me (or anyone) he owed the IRS over $100,000 dollars and I didn't find out why money was so tight until we had been together almost four years.
My ex best friend shopped herself into $50,000 of credit card debt without her husband knowing about it.
If he won't talk to you about it, there is zero you can do other than find help for yourself to regain your balance. Therapy, support groups. For you. You have no control over HIM.
I agree with Ann 100%. Protect your own monies, and good luck. You may want to do a consultation with a financial planner or attorney.