Alright what should i do?

So i have this pet monkey named Charles and i have had him since he was 3 years old. Usually he is well-mannered, but recently he has been smacking me in the face for no reason when i walk by. I try to hit back but then he just spits at me. I don't know what the hell his problem is, and i'm tired of being treated like dirt by him. What should i do, because i really don't want to have to release him into the wild?