Drama with friends

My friends are acting mad wild! and its starting to put a strain on my enjoyment of chillin with my other friends. there basically acting like little kids okay a true example of this would be if i want to go out with my two best friends just together and they find out about it they get upset because they feel that they should have been invited all along. but when they go out they don't invite us. basically stuff like that. it's been going on for 6 months. and i try to act nice and treat them the way they want to treated but it's so hard. I need some serious help.!