I can't offer much help I'm afraid but I can identify 100% with what you've both said. It's so clear from reading your posts though that it's the depression talking, and not you as a person Mechanical. (Not that I know you of course!). Someone who isn't depressed would never even say those words, so try and keep in mind it's not you and who you are.
I don't know if that's any help. It helps me a lot to remember it's nothing I've done, it's like breaking a leg, it just needs fixing. I know it's more complicated than that (bastard thing!) but it helps me keep it in perspective when I feel like I'm drowning. I'm sure upping your dose will help you through the worst, keep talking here x One day soon you will wake up and you'll be grabbed by an idea, something you want to do, and you'll be onwards and upwards.
When I first talked to my doctor she asked me a similar question, I think she asked about anything in my life I 'take joy from'. I must have looked completely blank! I said I felt like I had just simply checked out of my life, and was basically going through the motions, and perhaps not even managing that.
Have decided I'm going to ring my doc on Monday and hopefully speak to her then or Tuesday (ridiculous new surgery system). I'll be saying that I feel I'm going backwards, and HELP! Dreading calling though, hate phone calls!
Take care of yourselves everyone xx