At the very least, stop putting off the "new" stuff that comes in. Open your new post daily and deal with new telephone calls as they happen. Don't put it off, just deal with it, whether it's paying a bill, completing a form, or whatever. At least, then, your "backlog" isn't getting worse. And dealing with each day as it happens is perfectly do-able.
Then, once you're successfully dealing with new/current stuff, you can start to chip away at your backlog - maybe just one bill or form or phone call per day from your "outstanding" matters. After a few weeks you'll be caught up.
You'll never ever catch up if you keep trying to make lists, and work through your backlog from the oldest first - you won't be motivated because you'll still have it in your mind that you're ignoring the new/current stuff, so it will be a never reducing "pile" which will just feed your anxiety and keep you demotivated.
Far better to draw a line under the past. Deal with new stuff quickly and efficiently as soon as it happens, which stops things getting worse. That'll help reduce your anxiety and give you a warm feeling. Only then can you go back to before the line and start chipping away at it.
As others have said, get your bills, car tax renewals, insurance renewals, etc., all done automatically via direct debits. You'll then know they're paid and you won't have to worry about forgetting to renew/pay, etc. Yes, I know it's not very "money saving" and you should be getting comparison quotes, etc., but you've bigger problems at the moment, i.e. the fines and missing deadlines which have to take priority. Once you've got control, you'll then have time to shop around, etc., next time around.
I speak from experience. I run my own business and was "waaay" behind with my own administration. I had piles of unopened post, piles of documents waiting to be filed, constantly fire fighting and having to be reactive only to the clients who shouted the loudest. It was a very stressful, costly and anxious few years. I'd spend hours looking at the piles of stuff but not actually doing anything with it! I turned it around by just putting all the piles of paperwork and everything else in a side room and shut the door on it. Then I adopted to "one touch" approach to everything new, whether post or emails or phone calls - I either dealt with it there and then, same day, if it needed attention (none of this putting it on a list to do tomorrow!), or if it didn't need doing, I binned it there and there. So my working day became entirely orientated around what post, emails and phone calls I received that day only. Obviously, some of the older stuff became urgent and got dealt with same day, when I received a reminder or irate phone call etc. Over a few weeks, because I was keeping up to date with new stuff and reminders for older stuff, there was less and less that was overdue and I started to have spare time in each day, which I then used, at the end of each day once my new work had been done, to start to chip away at my side room, which was then mostly just filing or shredding. I've never gone back to the old ways. Still, some years later now, do everything immediately when I get it, which means a massive reduction in documents, emails, phone calls, etc as nothing is outstanding, so no reminders, final demands, etc.