Blowin' Smoke

My boyfriend, John, and I have an amazing relationship. We have known each other our entire lives and have been best friends for years. Our relationship is exactly how a lot of people want theirs to be--we share secrets, dreams, fears, and inside jokes. On top of our amazing friendship we share a complete infatuation with one another. I've never been in a relationship where I've felt this way (and I dated a guy for two and a half years, so I thought I knew "love"). Being with John is just so perfect... most of the time.

Of course, there is no such thing as a perfect relationship, I know. We always have a good time together, making everyday occurrences adventurous and fun. He is one of my best friends, but I have a problem. 

John used to do a lot of drugs--from smoking weed to popping pills. He stopped all of this before we even began dating, though, so I haven't seen anything of it. He still drinks alcohol, with friends, sometimes on the weekends, and I'm okay with that as long as it doesn't get out of control. Once, though, I made kind of a big deal about his drinking, because he seemed to be doing it so often and he'd told me he wanted to be healthier. So I'd thought, 'isn't that a bit of a contradiction?' I don't really drink, myself (I can actually count on one hand how many times I have), so it's sort of a weird subject to me. 

Anyway, similarly to drinking, John used to smoke weed. We've talked about it and he's told me that he'd quit before we'd started dating. I completely believe him, too. The problem is this: I saw, on a friend's Instagram, that John was tagged in a picture of a hookah pipe. It was a friend of his, who he'd told me he was hanging out with, so that made sense. What bothers me is that I don't know if John was smoking that night. He never smoked cigarettes, only weed. And I understand that hookah is a somewhat healthier alternative in tobacco smoking, but I don't get 1) why he would smoke it and 2) why he wouldn't tell me. He'd said that they'd played a game at his friend's house. What worries me is that he may be doing things and not telling me solely because he knows I disapprove. Sure, I may not like it, but I'd rather him do things I don't like and tell me than do things behind my back. I asked him about it and he acted like he'd had no idea. I want to trust him, but I'm confused. 

So, what do I do? He's not only my boyfriend, but my best friend, and I want us to be completely open. I'd thought we were, but I may be wrong... Help!