Wow, Muon, I'm so sorry your symptoms are so bad, I can imagine what it feels like because I also get symptoms even just with sexual arousal, which is weird because being a woman there shouldn't be any precum being produced... Maybe the natural lubrication fluid is the culprit in my case? Anyway, my symptoms after arousal are mild and nothing compared to a full POIS episode, but as my POIS has been slowly but steadily getting worse with time, I'm really afraid that at some point in the future I might develop such a strong reaction to arousal as you have. Because if that's the case, considering the severity of my symptoms and my very high sex drive, I'm pretty much dead. I've had a fever as high as 40?C (104?F), and doctors were worried I might start convulsing.
Anyway, sorry for the rant. I really hope we can find the cause someday. Wouldn't it be nice if it was something easily treatable like some kind of pathogen that was causing the issue... But I'm less and less hopeful every day.