I think that you should let it go. The best revenge is being happy and ignoring his bullshit. the only reason he is saying shit about you is because he knows that she still cares about you and that he can't do shit about it. He's jealous. He may have her in his bed, but you're in her head. That rhymed...be impressed. Let it go...and if you see him...just smile because you know you are better than him. That's my advice...