Cheating?

Okay so my fiancé cheated on me, so I cheated on him....wrong I know, but I was angry and thought revenge was a good choose, I regret that now. I love him with all my heart and I've been trying to prove that to him, but no matter what he ALWAYS thinks I'm cheating, or texting someone else of whatever! A realationship without trust is nothing, and I keep telling him if he doesn't trust me then he Gould just leave because it's killing me....I know I really  hurt him when I cheated but I promised to never to that again, I'm trying to build back trust with him but it's so hard, I feel like hates me...what should I do? This happend montha ago, why can't he get over it? I got over I when he cheated..why is this any diffrent??