If I understand your post correctly, it's that you initially wanted him to drink with you for fun, but after the truth came out, you want him to do whatever is best for him. That's respectable of you, but if you can truly see how much alcohol destroyed his life in the past, I think it's no secret that he shouldn't drink again. I understand you not wanting to tell him what to do, but he is your boyfriend and you're obviously thinking of him first. It doesn't have to be a lecture, just tell him you're worried because of what he has told you, and you personally don't think he should start drinking again. As you said, he has feelings of guilt and shame even now when he drinks. The reason a person would continue drinking after having these feelings is because of alcoholism. Most people on this website (myself included) would understand that!
I hope everything works out for you.
