My Best Friend Has Become a Stranger?

it sounds like he's really deep into his own little world- he's never been in a healthy relationship as it sounds. His attachment to the girlfriend is more than it should be- a couple needs to have friends outside of the relationship (or at least one). If he turns away from you an further it seems like he won't even be talking to you at all..which is sad. His life is taking a turn inward and instead of growing up and maturing he's recoiling and his world is becoming smaller- does he have a job? Maybe you could meet up with him after work and try to talk it out- as long as the girlfriend isn't around. He is placing a lot of value on his time with the girl which would be okay if he were keeping at least one old friendship alive. I think he is possibly obsessing. The most that you can do is try to talk to him, but recreating the old times is probably not going to ever happen. Sometimes people grow distant because they can't develop their lives any further and in 10 years he will just be a control freak with no life outside of the woman and work. It's his destiny and if you lose the friendship then it's not your fault.