Childhood depression & ADHD

I'm not entirely sure if I have anything, because frankly I don't trust my own judgment. It could be typical experience, but it doesn't feel like it.

I'm about eighteen right now, but since I was younger (I can't remember exactly when it began, possibly around 16) I began to experience very unpleasant lows which tended to last up to a few days, and they were far more prevalent than anything else. A "good day" to me is generally a day when nothing significant happens to trigger these feelings, and they are triggered relatively easily. Their intensity runs the gamut from ordinary sadness to an almost crippling feeling when I find it difficult to converse with people. Hypersensitivity is also an issue, as relatively small events could conceivably set me on the wrong track. Talking with others helps, but ineitably I always return tot hat state of hopelessness. There has also been a great deal (multiple times daily) of suicide ideation, though I do not consider it serious planning. I have always entertained it as a last resort, however.

A lot of it does seem to stem from anxieties and insecurities I have. I have for a long time been considered "gifted" and have a long history of academic achievement, but I do not feel as accomplished as I probably should, and I always fear for the worst in my courses. Last semester, I thought I would fail but ended up with almost all As. Over the summer, I had a panic attack at my job working a concession stand, which in retrospect was a relatively minor job.

I also feel chronic feelings of loneliness which my friends can not always solve. There was a bad breakup I had this summer after which I had a drastic change in mindset, becoming far more pessimistic about my love life and almost convinced of its failure. It especially pains me to see others together, and I consider my shyness to be a major obstacle.

There has been a great deal of pessimism that has been a common thread through my life, but recently it has been "legitimized" so to speak. I consider myself a nihilist of sorts, and I have recently been quite vocal in my belief in an inherently hostile world. Most alarmingly, though, I have entertained thoughts justifying my condition as being a means of natural selection, with me being selected out. I know it sounds ridiculous, but at times it has seemed plausible.

I do have something of a history. My father's side of the family has been known to have problems with bipolar disorder and schizophrenia, and I myself was diagnosed with childhood depression in elementary school, as well as ADHD earlier on. I am concerned, as my symptoms have intensified and become more frequent in college, sometimes reaching intolerable levels. I am unsure if this is diagnosable, but dysthymia seems to fit to some degree.