I'm saying that because that was the case for me. A back then undiscovered dose of mercury led to all kinds of back then mostly ignored ("it's not that bad and it'll probably go way" - I was young) issues, and some tinnitus was just a part of it, but also some serious sleep issues.
Any such environmental factors are rarely diagnosed, because that's really hard unless it's so bad that it's severe acute poisoning. But any less than that probably won't ever be discovered and will all be attributed - by the person themselves too (in my case definitely) - to "stress" (even if there is not that much) or aging. You can't detect it with imaging, symptoms are inconclusive at best, and forget blood tests, they are only useful for said acute poisonings.
> and only dream here and there
You would not know if you dreamed, normally. Only if you wake up while still dreaming. Even then usually you quickly forget most or all of what it was about. To remember more you have to wake up right in the middle of it.
By the way, speaking about dreams, during the years when I had those issues my dreams often were nightmares, they were full of feelings of helplessness, being unable or barely able to move, and generally very unpleasant. I had more than once during those harder times dreams where parts of my body were very seriously diseased including total tissue disintegration and open holes in my body, inside the dream.
Those dreams came from "below", from the "hardware", not from my (completely unconcerned) consciousness (I hope I kind of get across what I mean, not sure how to formulate this correctly). What I mean is, at the time I had no worries about my health whatsoever. All my problems, even though something like almost-asthma allergy coming out of nowhere and suddenly, seemed normal and manageable and as if it would all go away given some time, so I just coped (for example, hyposensitization treatment) and worked around the issues but didn't think much of it.
Since the problem was actually diagnosed (university clinic, lab tests) and solved (chelators, for years) my dreams have become AMAZING, and super interesting too. I'm so glad I had to wake up during some of them (alarm was set) so that I actually remember some. I never knew what great fantasies, sophistication and city-, house- and landscapes my brain was capable of generating, it was just terrible before.
Given that experience, I think even if it's kind of useless because it's way too vague and probably very dependent on the individual, the contents of dreams might give some indications to a body's health status too.