My boyfriend cheated on me, and it kinda turns me on..is this normal?

Hello,I walked in on my boyfriend of one year cheating on me almost 8 days ago...I am trying to power through it, because he feels really upset at what he did and he’s making tremendous efforts to repair the relationship.My question is this, I am truly devastated that his happened. I am 21 and he is 19 and it was the first real relationship we both have ever been in. We love eachother. However, I have jerked off multiple times to the thought of my boyfriend getting fucked by this guy.... is so confused.Any help is appreciated.Thanks.