Hi prefab
Thanks from me for sharing how you're doing..........and it doesn't matter how badly you feel in comparison to others.........if you're struggling, you're struggling and
that matters, what you're going through
matters 
Real good idea to get checked out by your G.P. although it also really does sound like depression could be there..........at least some of the symptoms are
definately there.
I wouldn't say it necessarily makes it less "bad" that the sadness isn't there (or doesn't stand out?)...........the lack of interest or enjoyment in things, the inescapable fatigue, the flat (apathetic?) feeling...........they're hard enough to cope with, right?!
And can be signs of depression in themselves..........so good you're getting them checked out.
But how to get things across to her properly.........I'd say you've done a great job explaining it on here, so if you could tell her all of this..........even write yourself some notes to take in with you if that helps too........maybe there are even some other things you've pushed to one side, even if they seem "minor" they could count/matter e.g. slight changes in appetite or sleep patterns etc.??
And a little diversion.........your job/low paid/low status/"failure career wise"...........I am sorry you're not in a place you want to be right now.........but to me.........
so many "low status" jobs are
massively under-rated and the people doing them should get
so much more credit, because they
are important/the people doing them
are important.........so whatever you do..........stick stamps on envelopes, deliver mail, serve food/drinks. conveyor belt work, collect refuse, sweep streets, whatever.........prefab.......I'm saying what you do can really matter, I'm saying that
you really matter
And maybe, now I know this may be hard with the way you're feeling, but maybe you could do something different, something you might find a little more satisfying in your "free time".........could be anything..........reading, writing, listening to (more?) music, watching films, something a little creative.......??? Just a thought.............
But, hoping it goes well with the G.P. and even
if it turns out that isn't depression then you're certainly feeling in a lot of ways like a lot of people on here..........so stick around.........and I'm sure you'll get plenty of support on here
Alison