For the past few decades - since puberty or thereabouts - I started to smell something unpleasant and it wouldn't go away no matter where I was, or how recently I'd had a wash, leading me to assume it must be me and that I simply smell.
After suffering for a while I finally reached out to family and bosses at work and of course their response was that I don't smell, which was news to me. I had assumed I stank and everyone was awfully politely putting up with it.
Spoken therapy and CBT helped a bit, but being the NHS it trailed off in an unsatisfactoy fashion and so I dealt with it myself over the years by becoming a hermit.
Later in life I paid for further spoken therapy and was prescribed an SSRI anti-depressant and that finally put me on the path to not smelling bad smells more often than not. SSRIs of course have side effects which aren't fantastic, but it's better than the godawful feeling that you stink!
I feel for the author who dealt with this on top of tinnitus.
It's not often that I get to talk about this, if anyone has any similar experiences I'd love to hear about them :)