He cheated years ago (really long post)

So I was dating a guy and we had a pretty rocky relationship. He was immature and iffy on commitment. He would call me names, was paranoid about me cheating, had extreme anger issues and so much more.

We dated 3.5 years and it was getting to the point I was ready to end the relationship. He went on a trip and when he came back he told me he met someone and she kissed him and he was sorry. I ended the relationship because I wasn't happy anymore and I wanted him to have the freedom to explore with other people.

We remained friends (in a loose sense of the word). He caught her with another guy and a couple of months later he asked me to get back together. He said that he realized as soon as we broke up that he screwed up and he wanted to spend his life with me.

After a while, I realized that he was a completely different person. Completely dedicated to me, respectful, kind, thoughtful, etc. He wanted to provide for me and treat me right. He didn't yell or argue; he wasn't paranoid or pushy. We later got married and built a wonderfully happy marriage.

Two years into our marriage, I get a message from that girl (he doesn't call her his girlfriend. It became clear that he had an ongoing affair with her. He met and started a relationship with her months before he went on his trip when he said he met her.

She has made our lives hell to the point that lawyers and cops are involved. It's our lawyer's opinion that she messaged me because she found out he was married and got mad about it. She wants him to herself and is angry he ended up with me.

My problem is that even though he has been so wonderful since we got back together, but I feel empty since finding out. I feel like it just happened. I feel like he was two different people. He has proven to me time and time again that he's 1000% devoted to our relationship.

He's open with his phone, comforts me, and listens to every single rant and emotional tirade about my pain over the affair. He always offers proof of where he is and what he's doing.

I have never checked up on him and I don't care to see proof. I'm not a jealous person at all. Overall, I'm so thankful for our marriage and the person he is now. I simply don't know how to deal with the devastation of the betrayal.

Once in a while I get an image of them having sex. I am sometimes reminded of the lies he told while they were together. When He sees me sad he holds me and listens. I really want to find a way to move on.

Any advice about how to heal?