Danger danger, Will Robinson!!!
Of course he's using. And yeah, I hate to tell you this but coke and illicit sex almost go hand in hand. Viagra would be a BIG indication. On the gay party circuit (i am not implying that your husband is gay/bi, only citing an example), viagra/meth and viagra/coke combos are very popular. Unfortunately those combos cause unintended death fairly often for the very reason you sited: high blood pressure causing heart attack or stroke.
Do what you need to do to protect yourself and my suggestion is to you is: get tested.