Burning in anal/prostate shortly after ejaculation during sex. Going on for 2 years. No history of stds. Would herpes cause such a quick reaction?

Not herpes. It sounds like you might be having some dysfunction of the seminal vesicles or prostate that provide fluid as part of semen during ejaculation. I suggest prostate exam and possible semen exam to test pH and signs of infection. https://en.wikipedia.org/wiki/Seminal_vesicle.