Breakup. Want to get back with him.

So my bf and I broke up on Sunday. He has changed so much since last June when we first started dating. We almost made it a year. . . I really still love him and want him back. . . but see the thing is I messed up in the beginning of our relationship by talking/flirting with his cousin on Snapchat. . . which I told him on Sunday what had happened. . . I ended that flirting like months ago but his cousin would still flirt and send me provocative pictures bit would apologize when I wouldn't reply. . . but anyways my bf back in October got drunk and his cousin (different cousin) invited a girl to stay the night at my bfs house with them. . . but my bf ended up laying on the same couch as her. . . he said nothing happened but i saw some of his texts between him and a friend of his and how my bf had blue balls. . . and my bf smoked weed and did other drugs behind my back . . . and he messaged a Canadian girl one time hello,g her she was hot. . . when i confronted him about it he said that he thought it was me. . . (but she looked nothing like me) . . . soooo. But after finally confessing to him what all occurred between his cousin and I . . .he told me he couldn't forgive me and called me some names. . . but I want him back. . . I love him. . . only thing is that he blocked me on all social media. . . how do I get him back?