I need some good advice.

[me]

I had this friend, then asked me out, anyway its a long story. It was
the biggest mistake I've ever made. Now he thinks that I hate him
because I haven't really talked to him because I have been afraid to.
Lately he has been calling me all sorts of things that he knows aren't
true. I have changed a lot and I need him to know that so that maybe I
can have my friend back. Everytime I try to talk to him he just laughs
at me and everytime his sister talks to him about me he laughs too.
All of my friends agree that I haven't done anything wrong. His sister
is one of my best friends but she doesn't like talking about him and I.
Why is he acting like this and how can I get through to him? Please
send advice as quickly as possible!!!
Thanks!