Could you talk to T about that incident before the hypnosis? Then you can get T's advice about what you need to do now about that past indescretion, and T will know not to ask you about it under hypnosis.

For something that happened years ago when you were weak, depending on the circumstances at the time and the strength of your marriage since then, maybe it would be something you and your husband are able to deal with now if you are open about it, or maybe it won't be necessary to say anything to hubby. I think the pressure of keeping that secret all alone without support will wear on you though, and keep you from healing entirely. It might be something that T can help you with.