What the hell just happened?

Telling and retelling the story of this relationship and it's demise is exhausting and painful and I should quite like to stop, yet I can't, as it's been my single minded obsession since the first discovery. 

Finding out that my boyfriend had a bizarre little "relationship" with a 22 year old college senior for a few months was awful. He says he was unhappy, and yet he still went forward with our plans to move in together, for me to move my life for him. We started counseling. 

As I began to grasp the depth of his lies, I also rationalized that the occasional check of his phone and email would only help reassure me that he didn't have anything else going on...but I knew in my gut that I'd missed something. 

I had. Something much, much larger. The "casual friendship" he maintained with an ex fling that he'd alternately hidden and lied about was not casual, nor just a friendship. If only I'd gone just a little farther back in his texts the first time I looked, I'd have seen it all right away and known that not only was he sleeping with her, they would talk about me and the other girl and laugh about the whole sick situation. Not only that, but his conversations with this person showed B in an entirely different light - a mean, cold, bigoted asshole. 

Ending things threw my life into a tailspin - barely able to perform the most basic functions at work (I cried over a complicated expense report), dealing with HR about moving, explaining to my friends and family that I'd need to return home to get a handle on my life again...it's all a little more than humiliating. The only thing that provides any relief is talking about it, telling my story, like an antiquated attempt to bleed a patient to balance the humors. 

In my mind, it's done. The trouble now is reconciling the man I loved with the one I now know, working toward forgiveness, and moving on.