The only STD cause of testicular pain is acute epididymitis due to gonorrhea or chlamydia, and there always is marked enlargement and tenderness, almost always of a single testicle, not both; the standard gonorrhea or chlamydia test always is positive; and failure of your pain to improve after the initial treatment (the "bum shot", i.e. ceftriaxone, and oral doxycycline) are 100% effective against gonorrhea and chlamydia, respectively. Non sexually transmitted UTI also can cause acute epididymitis, but the nature of your testicular pain doesn't fit. Bilateral testicular pain, without signfiicant tenderness or enlargement, indeed can result from prostatitis, but urethral discharge usually is not present. Prostatitis is rarely due to any known STD. Most cases are not due to infection at all, but to non-infectious inflammation of unknown cause. It is common practice to attempt treatment with a broad-spectrum antibiotic like sulfamethoxazole-trimethoprim (Bactrim), but usually is doesn't work -- i.e. prostatitis continues.