Oops I meant to say kidney/yeast infections CANNOT make parasites from nothing.
Trichomoniasis is a parasite that is transmitted the same way as any STD. Men can carry it for a "long time" (never been able to figure out how long) without having any symptoms, if they ever have a problem with it. Because it isn't a fungus or a yeast it has no association with a yeast infection (although it might be able to mimic one or perhaps even cause one). Similarly, the kidney infections might have been caused by trichomoniasis, I'm unsure. However kidney infections make the parasites come from nothing. Likely your partner carried this without knowing, as there aren't very many obvious symptoms of it, and passed it to you.