I feel for you in your predicament. You’re plainly a thoughtful person who has come to what you feel are objective conclusions which make you feel worse about yourself, regardless of what your colleagues may say.
I would, however, urge you, as other commenters have, to allow that your frame of mind at the moment means that you’re not putting sufficient weight on good news or feedback but on the bad instead and that, as hard as it may be to try to separate your feelings about your job from the facts (which are that your co-workers and manager are kind, happy with you and and your pay and conditions are satisfactory) these are true, regardless of whether they feel true.
All that said and as Allison says, you don’t have to persevere in a job that makes you unhappy – if you can think of aspects of the job or roles in the past that you enjoyed more, then maybe it is time to hunt down something more compatible.
Also, just because your present pay and conditions suit you, in the post-Covid world it shouldn’t be impossible to get something else that fits these criteria. If job hunting feels daunting, narrowing your focus as much as possible to positions where your particular desirable criteria are built-in, can make it easier. I’ve heard this described as burning down the haystack to find the needle.
I see that you’re working from home and I get the impression as some of the other readers do that this means that difficulties you’re experiencing with your work could be easily addressed if you could just ask someone in the flesh as they arise. Plus, when you do seek help, it may be that due to remote working, it’s not being delivered in such a way as you will easily absorb (people absorb information differently and by e-mail or whatever, may not be optimum for you)
You obviously have mental health issues that you’re aware of and, presumably, addressing, however, it may be worth considering the chemical factory aspects of our bodies – isolation produces stress hormones which prime a person to react to threats. Obviously, most of the commentariat of Ask a Manager don’t live in the same dangerous world our ancestors evolved into but, as they say, our brain’s primary purpose is not to make us happy but to make us survive.
I may well be completely wrong here but if you are quite isolated then, in addition, to pre-existing mental health issues, you may also be reacting to over-production of stress hormones. If possible, could you try returning to the office for a few weeks as a sort of experiment to see if it helps? Perhaps you could say you have contractors in to deal with some sort of maintenance issues at home which makes it difficult to work?
It might not change your feelings about your job not being right for you you, but it might ease some of the stress you’re under and make it easier for you to clear some head space and make some changes.
