I think there is a difference between telling the truth and sharing every detail.
Telling you "I had sex with that person" is telling the truth. Sharing how the other person liked it, what they look like naked or what they did exactly is sharing every detail.
Sharing every detail is fine if everyone is on board with it. If people aren't, though, it becomes their private life. And you have to take a long, deep look at the situation, and realise that it is none of your business. And every one of your partners needs to realise the same thing.
And so, when something isn't yours to share, keeping it quiet should not be a torture, because it was never yours to share anyways. It belongs to the other person, and you can't betray their trust.
I suggest you have a long talk with everyone involved to see together what is or isn't cool to share.