Am I The AssHole?

I did not think about my affair with the girl, let us call her Pam, when I was in a situationship a few years ago. Since we had not discussed our exclusivity, Pam and I were just sexual partners with no conditions. I once decided to visit her to get some sex because I was feeling a little horny. When I arrived, I discovered her with another man, and for some reason, my jealousy overcame me. Pam came over for some coitus a few days later, but I refused. She became irate and left, cutting me off entirely and blocking me everywhere. Was she or was I the jerk?