PLEASE READ. IM SO SAD

Hi
three weeks ago i kissed a boy that wasnt my boyfriend in a pool. my boyfriend warned me many times about this boy , but i was drunk and we just kissed. for the following weeks, he has been unsure about us and we've been on and off, on and off. this month was prom and his graduation. he took another girl to prom, made out with her and posted a picture on instagram with her. he then travelled to punta cana with his friends and he wouldn't stop texting me that he loves me and wants to get back together. he came back this wednesday and begged me if we could meet; i accepted. (we have talked about this a thousand times) he was really sorry and regretful so we decided to give each other a second chance. start over. he acted as if everything was okay until saturday; the day of his graduation. he didnt even bother me to invite me. he is afraid of the people, he is ashamed of me. I opened my heart to him once again and he broke it again. i know i made a mistake but its been 3 weeks and i've had been living a living hell. what should i do? ps: he havent talk since yesterday night.