My boyfriend and I broke up,and now he treats me like ****.What's goin' on?

Okay so I love this guy to death.We dated six months.And I've had a thing for him for a good 10 months.We broke up and this went on for a good two days with just nothing but sadness on both are ends,but then he wanted tried getting me back again.He cheated so I said I'd need to gain back trust before we could possibly make it official again.So,that went well for about a day,till he started being a douche to me.And now he treats me like I'm the one that did wrong to him.He says it's because he's trying to push me away.But why?When he was just begging for me back,and now he is trying to rid me.It just doesn't make sense to me.And he started being like this all in one day,when he said he wanted to marry me and spend the rest of his life with me before.He was a really good guy before too,and now he's acting like a complete bad guy.The way he's acting just isn't him.I don't understand what happened to him.We never argued before,till this point and we spent literally day and night together.I always told him how I could never imagine my life without him,and now he's gone.:( Everyone keeps telling me to let go,but even when I do try to..he's always on my mind,and when I think about him,my heart skips wild beats.And I miss him like crazy.And the less time I'm with him,the greater the pain grows.I know I deserve better,but it's like my heart is telling me otherwise.What is really keeping my heart glued to him is he was such a sweetheart before,and now he's the biggest *** hole alive.He even admitted to me that what he did was selfish,and that he knows he changed a little.I understand that he doesn't love me back,but I want to stop getting treated like a piece of ****.