I am DH best friend and only friend now (his oldest and closest male friend killed himself last year and had been living in the states for 6 years before that).
I have friends and acquaintances and a very large family. DH has a good relationship with his parents but when there are problems he will of course share them with me even if he has been asked not to as he wants to talk to his wife when there is a problem. This is fine I am happy to be there for my dh.
Unfortunately he expects me not to talk to anyone else about issues he brings to me even when they effect the both of us. I do not gossip and I am selective about with whom and what I share. I think as I was brought up in a big and messy family that I am much more used sharing news and problems. While dh had a small family and a relative that caused horrible problems with malicious gossip in a tiny village - this left him with understandable trust issues. He trusts me utterly but doesn't trust many of my friends.
This I can empathise with but it can be very trying - DH gets to share with his best friend and I have to bottle it all up as I don't get the release that DH gets from sharing iyswim. Maybe I need to start a diary? I am not sure I am going to be able to change him without therapy but I need to explain my pov and am struggling with it.