Help, suggesting what exams to do... I'm lost.

I don't even know where exactly to post this, but I need some help because I am really lost and don't know what to do.

I don't have insurance because I moved here in US not too long ago, so every expense is on me (But that's OK).

It looks like I might have some bacteria or parasite.. something that gets "activated" during an intercourse.
My partner and I seem to get sick every time after sex... we get arms/hands and legs/feet numbness, brain fog... we become irritable and angry.. we feel sick as if something is traveling through our system.
My partner feels it more than me, like something almost moves through his body.

We tested for STDs (better safe than sorry), I did PAP test, general wellness test... we took humaworm and other anti-parasites, we tried a candida diet (since most of our symptoms seem like the Candida Overgrowth ones). Nothing comes up and nothing is working.

I am desperate, I don't know what test to take... I don't know what to look for. I don't have vaginal discharge nor itching etc.... but after sex we both get affected, and my partner suffers the most.

What could it be? What test should I get? I am completely lost. Please help! THANKS