<human>: Well, sorta. My ex and I have been trying to work on getting back together since we broke up six months ago. Some background, I am 21, so is he, we dated for three years before we broke up. Very loving relationship, we were long distance for two of the three years and I always trusted him.

For about a month after we broke up we were still hooking up and he was telling me that he loved me. I spent my birthday weekend at his place (Thursday-Saturday), and dropped by unexpectedly on Sunday to grab a jacket. Walked in on him watching movies with another girl in his room, he claimed they were just friends and I believed him. Less than a week later they were dating, I was furious, and we didn't talk for a month. He broke things off with her and has been trying to get back together with me since then.

He has always been adamant that nothing happened between them physically and that she was the one that initiated the dating and the relationship. I believed him. Two nights ago we went on a bar crawl and I took care of him and brought him back to his place. I got him in bed and noticed his FB was open. I am not proud of what I did next, in fact I am downright ashamed of it. I went through his messages and discovered that he had been hooking up with the girl he briefly dated and me at the same time, and that he had initiated most of the contact between the two of them.

I confronted him in the morning. He reacted violently, grabbed my arm and physically removed me from his house, leaving bruises. He has been back and forth all weekend yelling at me for betraying his trust and then apologizing. I am at a loss for what to do. I know I shouldn't have been on his FB, but at the same time I feel better knowing the truth. I dunno, I guess I just needed some outside perspective on what happened.

Condense the text into a few key points
<bot>: Lurked ex's FB, discovered he was hooking up with me and another girl at the same time right after we broke up. Feel betrayed.