Welcome here. It may well be that Sophie's advice to contact our Coronavirus Mental Wellbeing Support Service can give you better advice than I, however I've faced the problems you talked abut which seem to me to be
inability to work regular hours
not being able to go to sleep.
plus of course being in isolation.
May I ask if you allowed out for any exercise? If you are please take it. Even if you have have never exercised before now would be an excellent time to start. Look on the web and see what is there free for people starting out, you do not want to damage yourself.
If you are not allowed out the same thing applies, pick a starter YouTube channel you like and follow thogh the exercises. don't overdo it but if you can feel tired at the end of the session you have accomplished what needs to be done.
Make a list of everything you can think of you like that's practical, music, reading, model-making, whatever you want.
Divide up your work, easiest ones first and go for half an hour, stand, do a moment's like exercise, then return for another half hour. Promise yourself a little of what you like to end the hour.
Divide up your day and resist the temptation to binge on what you like:). You may end up doing an actual 4-5 hours work , they will be productive ones. You may do less, but still productive.
Of the thngs you like keep the most relaxing one for bedtime -not a fast paced movie, maybe a book or audiobook. You can get umpteen from
https://librivox.org/ plus you may find eBooks to download from the web..
All free. The more soothing the better.
Being by yourself is never good and this is something umpteen in Victoria are feeling at the moment. Maybe you can pick up old family relations or acquaintances again who would like contact with you. Also The Government website
may have a list of ways to get to know people and chat, Please let me know, I'd be interested.
Hang in there