Wtf do I do?

I'm pretty sure my boyfriend gets jealous of the fact that I get along with his best friend. I don't have feelings for him (which I'm afraid he's assuming, even though it's FAR from the truth), he's just chill and fucking hilarious and my boyfriend would go "why do you laugh at his jokes but not mine?" "so now you laugh at his jokes and agree with him?" it gets irritating. My boyfriend likes to say that his friends are my friends but how can they be if he throws a bitch fit each time I get along with them? I invited him to celebrate my 21st birthday with us, and I think it was a mistake. Do I distance myself from him? Do I pretend he doesn't exist??? It's gonna be hard because 9 times out of 10, when I see my bf, his best friend is gonna be there too.