I have been in this boat (as far as I can judge from your story--I wouldn't tell anyone "I know how you feel"), in February it'll have been 10 years. Overworked myself during university (which took way longer than it should have, but everyone kept telling me "oh I feel like that sometimes too"--never did I realize they didnt have to deal with it every minute, every day). When the student loan ran out (back then
very generous in NL), I got a coding job, two days a week (trying to finish my study, except I was mainly recovering most of the week), after two months something snapped, I couldn't read the code on the screen anymore, scared the shit out of me (been coding since I was 9). Completely broke down.
I have tried so many things (therapy, meds, alternative therapy, physical checkup, coaching). No solutions. Anti-depressants make it more bearable, but they also seem to suck motivation (and have side-effects) so I use them on and off (for longer periods of course otherwise they don't make sense), recently I've been in a bad place so I'm back on again (which works but it's no progress either).
I wish I had some solid advice to give you. Your story is in fact the first time I hear something quite as similar to my experience (cause it's not quite like a burnout, is it?), except I never got myself to work the hours your post suggests you did, instead using--I dunno--intellect to make up for it, which just leads to perfectionism and pushed me over the edge just as well[0]. Except I wasn't aware I was asking too much of myself.
Going to re-read this thread tomorrow, maybe some of the replies have some good advice that I haven't tried yet (or might be worth to re-try). Never stop fighting, life's too amazing, even if you can't live it like all the other people.
Currently I'm doing the best I can, volunteering at several youth-centres, teaching kids as much computer / computational science I have learned, trying to put my education and knowledge to the best use as possible (also, turns out that teaching and working with kids is a passion of mine I never discovered in comp.sci). Even though I only have the energy to do it 12h/wk, I know I'm doing something amazing for these kids who will remember me when they're old. I also realize I'm super lucky to live in the Netherlands, in the US I'd be on the streets (this resonates http://www.iquilezles.org/blog/?p=2659 ), and possibly a dead junkie.
I wish you the best of luck and to somehow some day find happiness. If there's anything you like like to talk about, my email's in my profile.