Inflammation due to any obstruction?

From around 4 years till now, I started noticing there is a reduction in my semen while ejaculating, but there was no pain. I never had any issue with fertility or any STD history in the past. No issues with orgasm and erection. Since there was no pain, I was ignoring thinking it could be due to stress and my age (36 yrs old).

Other than these low ejaculation, I did not have any major issues in the last 4 years, and perfectly fine. But around eight months back I started getting constant, mild pain in my left testicle, some where on the spermatic cord slightly above the testicle. It worsens while sitting or wearing tight fit pants. When the urologist asked me to take ultrasound scan of the scrotum, it revealed there is very little swelling in the left epididymis when compared with the right epididymis with little hydrocele. But my urologist din't find any bacteria in the urine analysis, which is very clear. My testicle was also not seen swelled from outside, they appear pretty normal in size. I also started getting some burning wound kind of feeling little above the testicle somewhere on the cords, but not exactly on epididymis. The pain is continuous and constant, I am not having tenderness to touch every time.

This is making me think that the low ejaculation in the last 4 years indeed was some blockage in spermatic cord or epididymis coils which now became epididymitis? Can somebody share your view on this?

Since no bacterias found, can virus cause epididymitis? If so, what and how can virus gain entry into epididymis, and how long it will take to clear-up? I hardly had penetrative sex in nearly 1.5 years, and don't have genital herpes, chlamydia, gonorrhea, syphilis, etc.

Thanks
Nick.