How to explain to my girlfriend that it is not my fault but the masseuse who got me?

Something like this has never happened to me, much less with my girlfriend at home. i hire a masseur at home because my neck has been fatal for a few days. how wonderful when i lie on the table and start giving me the massage. suddenly i notice how he reaches into my pants and i can't resist. things get complicated and we end up fucking my girlfriend in the kitchen ...