What kind of depression do I have? Why don’t I get better?

Patient: I’ve been constantly depressed for years. It started when I was a child, can’t remember when. When I was 15 it escalated rapidly without reason and I became severely depressed (suicidal and started selfharming). Since then I’ve been constantly severely depressed. I’m 20 now, and this isn’t normal. An untreated depression only lasts for a couple of months, maybe a year. I’ve been in therapy for five years, without getting better. I’ve talked to over 20 different tharapists. I’ve been on fluoxetin, remeron, effexor and cipralex for months at a time without any positive effect. I’ve never experienced trauma and I had a good childhood (though I was depressed and had (have) social anxiety). All blood-tests are fine, and always have been. I’ve even got my brain scanned trying to find out why I’m so depressed, but everything was normal. Why am I depressed? Why don’t I get better? What kind of depression lasts for years?I dropped out of school long ago and I’ve lost all my friends. I only leave the house for grocery-shopping. I have no life. My brain don’t function anymore, everything is just one big grey fog. I can’t think. I don’t think I’ll survive this much longer…

Symptoms: Pretty much every symptom of depression, I’ve taken many tests and I always end up under severe depression.