I lost one of my bestfriends because he changed, and he did change, I think he thought he needed to act more tough and gained this strange fake "confidence", his entire outlook on everything changed from one of openness and acceptance to closed off and arrogantly objectful.
I'm now at Uni so I rarely see him now anyway, it's really great when I do see him usually because it's been a while lots of catching up to do etc, strangely enough he seems to be coming down from this state he has been in over the past couple years but I don't know if he is totally or if it will last.
My advice to you is, become independent enough to not need to rely on others, this is mainly my way of thinking and although I know isn't always the best way, it is the way I recommend to you in the sense of getting enough space from this friend, you may just need more time apart and not talk as much.. it's the same with relationships, it's good to be close but you are still individuals, and should go through life as such, always.