How can you get over a dead person?

My best friend died in a car crash an 3 years ago and since then he has been haunting me but why would he because we were the bestest friends before he died but he tells me ever since the car crash that I should never have been with another person that night he died and I was but he also says he blames the other person for his death when he(the other person) was the driver in the car at the time. Am I to blame or have I done something wrong. I cant tell anyone not even my parents about it they wont listen. Tell me what he wants.