ex boyfriend

I was w my boyfriend for over a year and a half . A few days ago I found out that he hooked up w a girl three months ago . apparently they hook up when me and him ‘ broke up ‘ but our break ups are literally like a day or less ( yeah I know its bad to break up a lot , but it’s really not as common as it was during that time of our relationship ) anyway , I found out they had sex and then me and him got back together and he never told me . I also found out that a few days after we got back together , we got into another fight and he went back to the girls house and had sex w her again . they also went to Utah I guess , but when he went to Utah w the girl, we never broke up , he just got mad at me and disappeared and I guess he was w her . anyways that was months ago and we were in a great place in our relationship when I found out what happened , but when I found out I left him and told him it was over . he tried to win me over that night and barely the next morning and then stopped texting me , a few days later he tried again and I was almost falling for it and I kept thinking of what happen and if I just take him back instantly he would just do it again . so he got mad and told me I was playing w him feelings and that if I want him I need to let him know and if I don’t he’s just gonna do him . ( he told me this not even 24 hours ago ) and now he’s already making plans w other girls . should I just move on or talk to him since he had sex w her when we broke up