I don't want to resolve things with my best friend
Can you tell me what went wrong?
I was so desperately in love with him and he didn't want to be my boyfriend. I got angry when he rejected me and we got in a fight
You can feel badly he doesn't feel the same. But he can't help it and you should resolves rifts with friends.
I'm so angry at him.
It's common to feel hurt and angry after being rejected.  You need to respect his wishes however!  Having him as a friend is certainly better than not having him as a friend, regardless of whether you two are dating, right?