Very foul-smelling stool, parasitic/bacterial issue?

Hi everyone!

I've been dealing with this embarrassing BM issue for a few years now.
My poop is having a horrible smell - it is best described as pungent and repulsive, just very sharp and poisonous. It is very different to usual smell of poo. I came across this smell for the first time in my life when visiting public toilets as a kid - this smell kinda remains in the toilet area and can't be removed with cleaners and deodorants etc. I think it's very specific and believe it's bacterial/parasitic due to the fact that the smell doesn't really go away after the stool has been flushed. Longer term stench could also have a bad fishy odour.

My suspicion is something parasitic but I haven't had any luck addressing the issue with doctors. Stool samples came negative. I am sure however some of you would know the smell I'm talking about as it's so specific and unique and indicative of an infestation in a person.
I did eat sushi just before getting this issue and also dealt sexually with a person who was carrying that smell, but when I found out it was too late and I now seem to have contracted it? He had this rotten fruit smell coming from his bum, which is not typical and later I found I've got it too and it accompanies the main nasty smell that's in the BM's.
Anyway I did have parasitic symptoms like itchy bottom, needing to scratch in my drowse, extremely poor sleep, insomnia, euphoria, alternating increase/loss of appetite and consequently losing weight without change in portions, extreme tiredness, weird moods, loss or huge decrease in sense of smell, and just general feeling of something gone terribly wrong with my body as it all happened within a matter of a month or two! I took some anti-parasitic medications like albendazole and mebendazole which had me having fishy smelling diarrhea, after that the smell returned to the nasty horrible one. I took a course of tinidazole too and that had a good effect for the first 5 days but then I started getting the psychiatric side effects and my issues returned. My pee later also started smelling very strong and bad, chemical-like? Urine sample showed up Klebsiella infection. I took a few rounds of Antibiotics but it hasn't gotten rid of it, although they made me feel better initially and more energetic, I think my poop smell improved too. I've often been having the little white speckles in my poo as well.

So any of you familiar with this smell? It's not that uncommon and at least one of you should have an idea of what I'm trying to describe. Any help much appreciated! Tweet