Best (guy) friend drama

My best friend is one hell of a guy! But here is the thing we have non each other for years (to be honest I can't even remember how we became friends) and every time I get a boyfriend he becomes this depressed child and starts being a dick and tells me that he is better then any guy but then when I was single he was just his normal self and when I would bring it up he would just telling me being friends is better!! But now that I am engaged to one hell of a guy that I love my best friend is telling me he loves me and is moving away cuz it's to hard to see me with my fiancé..please tell me I am not the only girl who has this problem! Telling me what you guys have done in this situation!