@Wolfcub, wow. I also got a flu like illness two years ago. I was nauseous for a few days back then and quickly recovered. The flu like symptoms reappeared 7 months after the first onset, but without fever this time. My stomach has been sick every day since then. My GI tract was completely healthy, until it just stopped being healthy. So strange, our stories are so alike. Did you get tested for enteroviruses?
Now the weird thing is that whatever "bug" I caught in March 2018 which started this whole thing, was never revealed. I didn't go to the doctor until the 4th week of it. He did a full health work-up but no nose/throat swabs. I asked about that, but he said swabs wouldn't show anything by that stage anyway.
I'd never had throat symptoms.
Bloodwork revealed nothing at all untoward and no signs of infection; only some very slight anomalies re: electrolytes. Those were not even bad enough apparently to warrant a "red flag" but the lab did mention them.
At the time I endlessly searched for clues as to what virus may have caused the weird "flu-like" illness (yes, flu-like....but not quite.) It was constantly afebrile, with no respiratory symptoms, just an endless (and then recurring at intervals) malaise just like I had flu.
So -no fever and a lack of other classic symptoms according to each infection, meant the illness matched no viral profile including the whole list of enteroviruses, and believe me I examined every single one. Any kind of flu was almost ruled out as there were no respiratory symptoms. Nobody knew what the heck it was.
What I had, which happened suddenly at a certain time on a certain date was:
slight but persistent head pain over right eye
a "fluey" malaise (a constant feeling of the first day of coming down with flu)
upset lower gut (in the 4th week)
loss of appetite (and sometimes incredible ravenous hunger and food cravings for canned sardines, butter, bread, chocolate, eggs....very often in the middle of the night, alternating with nausea.)
occasional "tight chest" which would pass within minutes, with some sharp chest pains.
weakness in leg muscles and sometimes complete spasticity in legs which brought me to the ground literally for about 3 mins. each time.
And a feeling of "sentimentality" where things would bring me to tears so easily. (music, movies, memories etc) This alternated with an empty feeling where I found it hard to connect with anything heart-felt, and instead felt a bit robotic, just enduring each day and plodding on with things I had to do.
(Heart checks were all okay) It was not a cardiac infection either, apparently.
So -what virus caused all that....I don't know. But it came on suddenly out of the blue and I had always been fit, strong, well, healthy, athletic, had a strong digestion....etc
My doctor also grilled me about possible clues as to it being poisoning of some kind, but that was kind of ruled out. Again it fitted no poisoning profile (and again, I researched every single one, including possible organophosphate/herbicide/fungicide/ or other toxicity from neighbouring farmland.) No profile described what I was experiencing.
And have been in a remitting/relapsing cycle for 2 years since.