Living with depression

I think the worst thing about living with depression is that no one really gets that the psychological part of it is only the symptoms of a disease.
People tell me I need to pull myself together and learn to cope with life's pressure like they did.
What they'll NEVER understand is that it is not life's pressures that get me down.
It's like a little voice inside my head that quite a lot of the time speaks what seems like sense.
Psychologists and psychiatrists alike keep on telling you that you need to challenge every negative thought you get.
When the depression starts to rear it's head EVERY thought is negative and bloody well most of the thoughts seem utter truth.
When you start to challenge every thought, especially when it seems logical, you get to a point very quickly where paranoia gets the best of you.
You don't know what's right and what's wrong anymore.
You can't make ANY decisions on your own because you start to find it difficult to distinguish between yourself and the "little voice".
I've tried to talk to people about it.
Not even the "shrinks" seem to really comprehend it.
What gets me even more is that at times I feel like I can read peoples' minds.
What scares me even more is that I've been proven spot on by too many people too many times not to trust my instincts.
Yesterday again I freaked out a friend of mine when I pretty much read her thoughts like she was saying them out loud.
Repeat: "I am NOT a Psychic"...check #19 on the next post....
The "little voice" takes advantage of that...
"He" allows me a moment of clarity to give me a bit of confidence in that "ability" and then he lets it fly with the negative thoughts.
It's like me against myself except the "little voice" part knows what's really happening and he's got his knife in for me and he's willing to break every rule to achieve my downfall.

Every day since I was 12 or 13 the "little voice" has been with me.
Everyday I've challenged it as long as I could, but I'm 33 now.
It's kept me from achieving anything in life.
Now there actually is something to be depressed about.
How do I distinguish negative thoughts from the truth now when even the truth really is negative?