Why does my ex still bother me?

If he's palling around girls that hurt me back in the day by dating guys that hurt me? I don't want to be associated with anyone that hurt me during a period of time when I got outed worse than Belle Knox at 15 because I got drugged and raped. At least Carrie from Stephen King wasn't drugged or mutilated.

I just want to get away from him, there's no going back to someone that put me down not knowing what I went through. I wasted enough time on a guy who will never love me and doubted me.