To think I'm being a good friend?

[Dumbledorker]

I'm friends with a couple. Let's call them Bob and Barbara....
So I was friends with Barbara first and we live quite close to each other and so see each other alot. In time Ive become just as good of friends with Bob too.

Last year Bob told me he needed to speak to someone in confidence that something was weighing heavy on him and he was struggling and didnt know who to talk to. He mentioned feelings of depression and despair but didnt feel he could tell Barbara the reasons to why because he was scared to death of losing her as he loves her so much. I told him that anything he confided in me with It would be strictly between him and me if he needed to get something off his chest and speak to someone. I was worried for him and was willing to help him. He confided in me that he was worried he was bisexual. Eventually admitting that he was and that he is struggling with shame as he cant stop thinking about men even though he loves Barbara. Hes feeling stuck and trapped and ashamed in himself as he has been brought up in a strict Christian family that were against homosexuality. I convinced him to go to his doctor to discuss his feelings and seek councilling. He completed the councilling and felt a little better but still feels in despair.
The problem is that I'm terrified of Barbara finding out I have been helping him. I feel awful as I have to play dumb If she speaks to me about him and his problems. If I tell her Bob has spoken to me I'm betraying my trust to Bob yet I feel I'm betraying Barbara by not telling her what hes told me. I feel awful

You are not betraying Barbara. You made a promise to Bob and you need to keep it.

You promised Bob. If Barbara is a decent friend she'd understand that having promised you stuck to it. Likewise if you promised her that you'd not say something then you'd be expected to keep quiet.

Completely agree with @Aquamarine1029 if you’re good friends with both you need to keep his promise.

I think it’s up to Bob to tell Barbara himself. It’s a very sticky situation but you made that promise.

You need to keep your promise, and if there's any fallout from Barbara you emphasise that if she asked you to keep something confidential you would respect that too.

If Bob is not acting on his thoughts your position is straightforward. If he is unfaithful then you are stuck between a rock and a hard place because Barbara will probably feel doubly-betrayed if/when she finds out. Is Bob's struggle and shame down to fancying men or down to cheating/wanting to cheat on his wife?

Its bloody awful honestly. I can only hope that she can see in the end that anything she has ever told me will always be safe with me. I genuinely have always always tried to be a good friend In this sense that I will keep to myself anything that someone has told me in confidence. I love Barbara so so much and hate that I cant tell her something this big but I do genuinely fear for Bob's life as he has become close in the past to ending it through this. That said I know that its sometimes important to break the trust if you think someone is in danger but with that in mind I have forced him to go to the doctors and councilling and also made him promise to always tell me if he ever feels that low again. My main worry is that if I tell Barbara everything it will push him over the edge.