The thing that make me irritated the most is the noise. With the kids without school, they're playing aloud most of the day in the street (even that in theory their parents shouldn't let them, for COVID reasons). For 1 day that's annoying enough, imagine after 6+ months working from home every day.
Also, the loniness (although I've still been seeing some family members and friends).
That said I am super-sensitive to external noise, especially my neighbour's dogs barking. My 'office' is also at the front of the house so any passing car (hardly any) can also irritate me.
My experience of watching my responses to external stimuli is that it all seems to depend on my underlying mood. ie. On a 'good' day I barely notice the dogs, but on a bad day it's like being flayed alive!
My feeling therefore is that the loneliness you mention could be why the noise is affecting you so much.
Here in Australia we are getting lots of TV ads about mental health and getting support, so it may help to visit your normal doctor, discuss it with them. and review your options. I did.
One thing I'd really recommend is making sure that you exercise regularly. There are great apps like Zombies Run or Peloton (there are normal workouts - bike not required) that can give you a great workout. They also have hooks to keep you engaged (storyline, Peloton's community) and help you maintain momentum. Strava has also been a great way to see what my friends are up to in a way that's toxic like Facebook.