Seven months ago, I cheated on my boyfriend and had sex with another man. I know many psychologists say that when cheating occurs, there’s something lacking in the relationship—but there was nothing missing. I don’t know why I did it, although the sheer volume of alcohol I consumed couldn’t have helped. It was inexcusable, but it cannot be undone.

Afterwards, I didn’t tell my boyfriend. Some people advised me that telling would only hurt him and destroy our relationship, and that it would be selfish because I would be the only one who would feel good after getting it off my chest. When I didn’t come clean to him, I was initially wrought with guilt. After awhile, I shook it off and have just been the best girlfriend and so grateful of him. Cheating was already out of character for me, but now I know that I would never, ever do anything so disrespectful to my boyfriend or our relationship again.

Here’s the tricky part: Last month he asked me to marry him, and I said yes. We’ve been meeting with marriage counselors and the priest who will marry us, and everything they say is about honesty, trust, partnership and honoring one another and our relationship. I feel worse than ever and I don’t know what to do. I’m afraid of telling him, because I can’t lose him. But I’m equally afraid of walking down that aisle and vowing to honor him without him knowing what I did. Should I tell?