You have been really sweet and helpful posting to my messages, so I'm gonna try and see if I can't help a little here. I go through those same feelings, and have also been battling depression as well as anxiety for over 10 years now. It makes it hard to see past your problems when they mount up in your head and eat away at you.
Any of the friends you've pulled away from, do you think any of them deal with the same struggles as you? Maybe you could give one a call and just in a nutshell let them know you're having hard times, and really want to reconnect. When I was deep in my depression, I also pulled away from everyone. One day I decided to call a friend of mine who had mentioned similar struggles, and we actually found comfort in talking about what each of us were dealing with and it really helped with the loneliness.
I don't know if that's an option for you, but it could definitely help fight the feelings of isolation. Because you are not alone - this msg board proves that, and some of your friends might be dealing with the same issues, and not know what to do about it.
I would advise against referring them here though. It might not bother you to have someone you personally know join this site, but it would keep me from feeling I could open up fully, knowing someone I know in real life see what I talk about here. If that wouldn't be a problem for you, then by all means do it!