"I want to hear your truth," Mountain Tim says with a kind smile on his face.

No, no. Don't tell him the truth. He wants to hear your truth. Wants to hear your side of things.

Not because he wants to hear both sides of the story. That'd be pathetic. But because he believes you. He thinks that his lover would never cheat on him without good reason or mistake. The idea that that isn't true isn't fathomable to him. The cowboy listens to his heart, and you've captured said heart.