Sorry posted too quickly before
I think definitely depression, but only because what you have gone through over the years echoes some of my own experience (both parents doctors but slightly bad at noticing or accepting that all wasnt well, the sertraline from a psychiatrist, the question of laziness or oversensitivity, thinking life is meaningless and general extended low feelings, issues with eating properly/disorderly eating).
I stopped using the sertraline to be honest I found it really odd that a psychiatrist just said "this'll help" except I'm sure from the outside it looks like you have a great life so why should u be not functioning well in the world and not seeing any reason to carry on.
The best thing that helped me (which I am doing now) is talking to someone on a weekly basis. There are certain things that you can go through (like when you said "Since I've been a teenager I've been quite lazy" ) and although talking about all this meaningly stuff seems like it wouldnt help for some reason, just like taking a tablet, it really does.
I still have this meaningless/pointless ting about life sometimes but at the moment i'm able to balance it with thinking about al the other things that give life meaning sporadically, like laughing about something with someone or making someone feel better, even if it's only for an hour. Life starts to mean more that way.
I mean everything you have described just sounds like real and true "depression". You parents might be the kinds of parents (like mine) who, although cared very much about me were a little too uncomfortable with addressing the issue of your general unhappiness and wanting to die - and would rather just pretend like nothing was wrong until the bank statement issue stopped them from being able to do that.
My depression got a lot worse after graduating - I felt like "right, I've done it. Life is done... what's the point in any more of this", like I kept my head down and now it's up, and there's nothing there worth seeing.
You shoudl talk to someone who knows really and truly how to listen to you. It's really worth it. Do you have someone that you speak to regularly? I can understand exactly why you are so weirdly affected by things like the news, and maybe certain things that someone (like family) might say could set you off?
Anyway just thought I'd reply since I sort of know what you are going through to some extent. Sorry you are feeling that way.