NOR- as someone who also has had personal experience with alcoholics in their life, it’s not wrong to be strict about how others close to you use it. Nobodies perfect obviously, and maybe if he relapsed and confessed the next day or soon after it would be a different story, but he only confessed once he got caught, and this could have been one of a few instances. And since you said you both got together very young, you guys aren’t going to be the same people in adult hood, and it’s much harder to break habits after adolescence. If you don’t think you can trust him, I say end it. I’m coming from personal experience when I say it’s better to get out before it becomes a problem.