Hi Martyn,
Since I read your message last night my head has been spinning around thinking of what I can write to encourage you. I recognise the perpetual stream of things to do, constantly being interrupted and loosing the thread with what I was doing.
Firstly: you mention dysthymia. I assume you have been to your doctor and got some support from that source.
Secondly: Do you have anybody to talk to who has your wellfare at heart? (Occupational health may be biased towards the company) Personally, I am taking antidepressants which dispersed the gray cloud which was hanging over my head. My improved mood also made me responding to counselling in a constructive way. The end result is that I am now doing very well, AND I am now talking to my husband.
Thirdly: Your work and explaining to bosses and colleagues. Depression and mental problems are subjects people find very difficult to talk about, and understand. (Did you understand yourself before you got your diagnosis?). As to organising your work so that it flows better, that is something you have to sort out yourself. If you have your own complaints of how other people are treating you ( with unreasonable demands), you might try to explain how you would like them to approach you. Personally, at work, nobody gets a sensible answer out of me if I am in the middle of a task. They leave me a note, and I then go to them and have a constructive conversation with them when my brain is free of anything else.
I know there is light at the end of the tunnel, and life is so much more comfortable once you are sorted out, but it is a hard slog. I think I am still inside the tunnel but the sun is shining on my feet (please, do not ask what time of the day it is, because the later it is in the day, the further in the sun will get).
Love and sympathy,
Ingrid