Depression is known to do that, and I'm sorry, but this is more than likely just the next step in your mental illness. I want to say "even I have felt that to some extent," but that sounds prideful. Hold on. Let me give you an extremely short backstory.

If you asked me to pick my most prominent personality feature, I'd probably say it was my empathy, and my desire to take the pain of other people into myself, so that it will hurt me, and hopefully not them. This aspect of myself was in complete and total control directly up until my depression got severe. I still have a lot of that empathy, sure, and the desire to protect the people I love is still there, but firstly, I'm broken myself now, and can't protect people until I get better. And secondly, I've found myself losing empathy for everyone but those closest to me.

That terrifies me to no end, just like it seems to haunt you. What I think I need to understand, and I think you do too, is that this is a part of the depression. It even makes sense. When you personally are experiencing so much internal pain, wouldn't it be natural for your body to decide that it can't take in the pain of anyone else, and so shuts off that valve, so to speak? The loss of empathy during depression is extremely unnerving. But it is a part of the process. It will fade faster if we simply accept that, and work on getting better.

Damn. I don't know how much I've helped you, but I think I needed to hear this.

To sum up, I'm so sorry that you have to go through this, but I want you to know, there is hope. Ok?