How do I help him move past infidelity?

I've been dating my bf for 2 years. For much of our relationship, I have suffered from his emotional abuse. I chose to stay. I still choose to stay. Now what I'm about to say is not to justify my actions, but it is my reasoning (poor reasoning) behind my infidelity, if in fact it is called infidelity. It was more of an emotional affair. In the midst of fighting, my bf would often threaten to cheat on me. He would name call and say horrible things to me out of anger. I believed every word he said to me. As someone who grew up in a good household, I had never experienced this type of "abuse". Not through my upbringing nor through any of my prior relationships. I didn't know how to handle it. I resorted to confiding in an ex boyfriend. I would be in communication with my ex, I'd sometimes visit him and stay at his home. Visiting him was over a span of 3 months. The communication was on and off for 1 year. He lived with his sick parents whom he was caring for. I spent the night there on 2 occasions and I slept on the same bed as him. Our relationship was strictly platonic. As hard as it is to believe, we've never been intimate with each other since our breakup. Though my feelings were made clear to him, my ex hoped for something more which I later learned. I'd run to him every time I had a fight with my bf and he would be there for me emotionally.

On numerous occasions, my bf would find call logs or evidence of my communication with my ex. The most recent finding resulted in my bf and not speaking for 4 days. By the 5th day, I decided to visit friends and family with my ex in tow. My bf happened to call that night. He said to leave and come home. No questions asked, I left behind my ex and went home to sort things out with my bf. This is where things became interesting. This angered my ex. He was under the impression my bf and I had permanently parted ways. He was so angered that I left to save things with my bf that he called my bf and told him he and I were sleeping together. He made up vulgar details. He told him of all the things I had confided in him about....personal things about my relationship. This conversation was filled with half truths and one single lie that has changed the dynamic of my relationship since. My ex planted in my bf's head I had been cheating.

Since then (about 3 weeks ago), I've cut off communication completely with my ex and his family. I am trying to move on with my bf to say the least. My bf is not taking this so lightly which is well warranted. He lays awake at night. He pleads with me daily to tell him the truth. He thinks I am being dishonest about sleeping with my ex. I completely understand that it's hard to believe an ex bf and gf can sleep in the same bed and not have intimate relations, but I genuinely say I did not. I innocently thought I had a true friend in my ex. He and his family were sort of scapegoats for me. Everything I was going through with my bf resulted in my lack of judgment. It was unacceptable. Since cutting communication with my ex, I am more focused on my relationship. I sleep better because my conscious is clean. The truth has come out and I am finally at peace.

How do I help my bf move past my poor decisions? How do I show him I am being honest? He is really suffering from this. He is depressed and has no drive for life anymore. This is constantly in the back of his mind. Will it get better over time? What are your thoughts?