Help! I have a wonderful boyfriend of two years, but he has an 8 year old son.?

I have been with this man for two years and he has a son who is currently 8 and about to turn 9. I have tried everything i can think of to make this kid like me. The mother of the child is not in the picture and hasn't been since the child was 2 months old. I let him and his dad have their time together to go do things as father and son. Also, i join in the family. We play basketball and the wii together, i go to all his baseball games, i help him with homework, he loves science so we do a few at home "experiments" together ect.. but this kid seems to still hate me! I just don't know what else to do! I talked to him about things i could do to help him adjust and he just hits me and throws things at me. I also went to his dad and asked him for help and all he says is he is just a kid. I don't want this to interfere with my relationship with his dad but i am afraid if it doesn't stop its going to.