What is the difference between clinical depression and dysthymia?

Hello doctor,

I am 18 years old and have been experiencing symptoms of some sort of depression for over six years. I did not realize that what I had been feeling was not normal until about a month ago. I currently do not know what type of depression I am experiencing, but I suspect it is either clinical depression or dysthymia. The only problem I find with dysthymia is that it is supposed to be mild with only two or three symptoms, whereas I am experiencing far more. I've taken ten different online tests and everyone came back as my level being severe or extremely severe. My symptoms are persistent sadness, emptiness, worthlessness, hopelessness, low self-esteem, and guilty feelings. Fun stuff like reading and drawing are not interesting. I can sleep for 12 hours and more and still be tired with feelings of fatigue and decreased energy. I overeat a lot and have noticed a gain in weight, everything seems hard, even the dishes. My memory sucks, along with my concentration. I get irritated easily and making decisions is difficult. Nothing has changed in the last several years, there are no 'good' days, nor any 'bad' ones. They are all the same, just that gaping hole of nothing all the time, every day, 24 hours, for years and years. Thankfully, I have not been cutting, nor I am suicidal. I have heard of double depression and it might be a possibility. I also suffer from social anxiety, if that makes a difference. If you could please enlighten me on this subject, it would be most appreciated. Please help.