How can I get my boyfriend to trust me again?

My first question is why should he? You broke his trust by hanging out with a guy you know he can't stand. How would you feel if he hung out with his ex that he's still friend with knowing full well you hated her guts? Wouldn't feel very good would it?

Think of how you would react to the situation and it's a good starting point for what he is going through.

Damn that's going to be hard for a guy to do, I would say even worse if he sees that guy on a regular basis. Trust can't just be built right back up after something like that, its going to take time there's nothing that you can do but just wait it out and don't get mad if he brings it up to win an argument.

I don't understand. You hung out with a guy who he hates and then broke up with you? What do you mean hung out? Do you mean you cheated on your guy?