Depression and lack of motivation.

I am a pretty sensitive guy. I don't get attached to things/people quite easily, but once I do, it's hard to get un-attached. I am having some issues with a friend of mine - well basically we aren't talking as much as I'd like to. Part of the blame goes to me as well because I am an introvert who can't make small talk and constantly need someone to initiate a conversation topic. And part of the blame, I believe, is shared by my friend who just doesn't seem to know that I am going through all of this and that I am having issues. Now I can't talk to her about this because I suck at confronting my emotions or talking about them with another person. And hence, this has been eating me up inside for so long now that I can't do anything without thinking of her. And there's always this sinking feeling in my stomach like I'm losing her or something like that. Can you please suggest any exercise or show me any other way, which I can incorporate in my daily routine to stop feeling so lonely?