I'm going to end a longtime friendship
Why do you want to end the longtime friendship?
It's annoying the way he talks about me behind my back.
I'm sure you don't like being talked about behind your back, but you might want to try to salvage the relationship first since you have been friends for so long. Try having a talk with your friend and tell him how you feel.
I guess you're right. I haven't really expressed to him how I feel.
Glad to hear you say that. It would be a shame to lose a long term relationship when an honest, respectful conversation might salvage it.