I cheated and i want him back. how do i get him back?

So friday night (3 nights ago). Me and my boyfriend went over to his cousins house. i dont remember anything from that night because i got more drunk than i have ever been in my life. when i woke up at home my mom told me that i was drunk and out of control and i ended up cheating on my boyfriend with his cousin after everyone went to bed. the thing is, i usually worry about him cheating on me since hes cheated on a few girls before (not me). im not one to cheat. like i love this kid with my whole heart. the 25th would have been our year and a half anniversery. Ive tried everything. calling him, apologizing, texting him. everything. he will not talk to me at all. so my sister texted him telling him how torn up i am and how he needs to give me a chance to talk to him face to face and try to fix things. he basically said his heart was broken and he is done with me. he said he would probably eventually talk to me about what happened, but on his own time. everyone thinks we will end up together, but im not so sure. weve been through a hell of a lot but nothing this big. i need some advice. what do you guys think? should i give him time to think? do you think he will ever forgive me? im a mess right now.