I'm very sure that I'm not unique here, and that a lot of other people will have experienced similar, and if I can talk about it they might not feel like I used to (and still do sometimes), like they were just skivers and just needed to knuckle down and get on with things and they were bad for not being able to.
Thanks for posting this Fridge, I'm sorry to hear about it, but it mirrors my own experience pretty well. You're definitely not alone and, now I know more about it, I think the problem is even more widespread that most people are aware of. It sort of crept up on me almost without me realising it, and admitting it was a problem in itself.
I'm lucky that I managed to avoid the full-on breakdown route I think, but like yourself I'd managed to literally worry myself sick and work was completely impossible (doctor's diagnosis of "stress" took about three seconds and was, much to my surprise, completely accurate; I didn't
feel stressed). I felt completely useless in my job (complete inability to concentrate) and was about to resign purely out of shame. Time off from work didn't help me much at all because the world was still a shitshow and I was still depressed within the same four walls.
Luckily I was able to pull myself out of that particular dive with a lot of help from friends and therapy (although it's not something I've been able to talk to my partner about constructively sadly). Looking back on it now (six months ago feels like a different world with a different me living in it) it's pretty staggering how bad of a state I was in.
I dunno if it's an option for you but stopping working from home was a big help for me. Two weeks after I got my second jab I started going back in to the office; even though there weren't many people to talk to to begin with, just having the routine and a change of scenery did wonders for my concentration, and work started becoming something I enjoyed again rather than something I was trying to run away from. Increased socialisation was one of the points on my action plan (I've been having pretty intense nostalgia pangs over the last year and have been missing a lot of old friends, including many from this site) and as much as it doesn't come terribly naturally to me I've forced myself to get in touch with some of them - even just exchanging a few texts saying hello has been a surprisingly rewarding experience.
From the sounds of things you've already made all of the hardest steps out of this rut. Temporarily losing access to your therapist must be a major drag, but I think you're probably beating yourself up about work. I was convinced when I told my boss I was going to need therapy that I'd be derided for it, but they were surprisingly accommodating - two of his other direct reports have also had "wobbles" similar to mine. I don't think there's any mileage in trying to hide it from them, because ultimately you're hiding the problem from yourself that way too, at least partially. If work value you at all, they'll not look down on you for needing help.
As kabbes says, this is wholly down to us all being handed a huge plate of shite and not some personal failing. Some people have dealt with it better than others sure, and I'm a little bit jealous of them to be honest, but the world is still a shitshow. The thing to hold on to here is your self. Take it slowly and take care
then they could sit in the 'breakout lounge' using WiFi, charging their kit and enjoying free coffee all day 
they are still as generous but definitely check it out. There are lots of shared office options but WeWork are at least very professional and offer a modern, clean work space without much noise at all.
