<human>: Can you give me the gist of the text in a nutshell?

Here's the back-story: He and I have been together for a couple years now and within the first year my sex drive slowed. I found it difficult to be attracted to him. When we met, I was not initially attracted to him and only wanted to be friends. Eventually it became more and I became attracted to him. As time goes on I fall more in love with him (who has admitted he wants spend the rest of his life with me) and find more things to feel proud of him for. He's become such a huge part of my life and I would do anything to make him happy. I've never cared about anyone like this before and I would do anything he asked me. Ultimately, he is my best friend. But here's where the story breaks bad.
Recently I have strayed and slept with another man. There's no justifying that act. We have discussed it and are working to move past it and build a better relationship. However, I'm afraid that this may happen again as a result of not being satisfied romantically. I'm afraid that I am not attracted to my boyfriend and that will damage the relationship further. What should I do?
<bot>: The attraction is lost for someone who I have considered a life partner, cheated on him, and now are trying to build a better relationship from the ashes.