What does 'projection of blame' and 'deflecting' mean?

My boyfriend of almost 4 years and I have broken up about a month ago. He still texts me mean hurtful messages and insists that the break up was all my fault. I told him that the door swings both ways, but he keeps saying that its my fault. Its almost like he is trying to hurt my feelings on purpose. Someone told me he is 'projecting blame' and 'deflecting' me. I don't understand what this means. I know and accept the wrongs I did, so why does ex boyfriend keep saying its all on me?