My bestfriend and me are spreading apart?

So lately we havent been the same. Also close friends of his have told me he hasnt been the same. He drifted into the group of fake people, theyll talk **** about anybody and pretend like thier bestfriends, he never make an effort to try to lets say text me and yells at me that i never text him when i do. he always thinks hes right about something. Whenever he hangs out with his "other friends" he never invites me even though i hang out with them to where we always meet up and he just leaves without tell me. After he started hanging out with the Sh**talkers its been different. i really dont know what to do...