I don't feel symptoms of depression in general though. I feel pretty happy with my current environment, my social life and hobbies are totally unaffected... other than the anxiety produced by the fact that I'm starting every day with a daily meeting where I have to communicate that I've done nothing whatsoever. But that's effect, not cause..
Several times in my life I’ve had bouts of what has looked like depression, but it was probably ADHD all along.
A psychiatrist might be able to help you to sort it out. (None of the GPs I’ve met had a clue about ADHD. Even my father is a GP and he didn’t have a clue either.)
For me, I had offered to help a colleague with a task that turned out to be much more overwhelming than I had originally anticipated (12 hours of reviewing legislation against our business systems). I got stuck oscillating between straining to do the task, and thinking that I couldn't bow out of it because I had already volunteered for it.
If you get stuck in a mode like that, where you don't have any dopamine hits from achievement and mounting anxiety, it's tricky to pull yourself back out. Being transparent with your team, and temporarily switching gears up to very (very!) simple tasks that you can complete, can help you regain your momentum.
People who are not inclined to psychological explanations would say "you need a vacation" and leave it at that.