I went to a party and kissed a boy. He never mentioned he had just broken up with his girlfriend.

I went to a party and kissed a boy. He never mentioned he had just broken up with his girlfriend. Two days later I go to town with him and my friends. His ex turns up with her friend, telling me how I’m such a slut because he kissed me and they attack me by punching me and throwing a drink at me in the middle of the street. I find it very unfair that I got attacked by some girl I never met. Now I wonder why I even liked the guy, and it makes me feel so low about myself that people want to hurt me because I’m a "slut."