Testicular pain that can range from mild to severe and nausea, are some of the orchitis symptoms (inflammation of testicle).
Most often, bacterial orchitis is the result of epididymitis, an inflammation of the coiled tube (epididymis) that connects the vas deferens and the testicle, and, epididymitis, usually, is caused by an infection of the urethra or bladder that spreads to the epididymis.
Acctually, your initial symptoms (frequent and urgent need to urinate with painful, burning urination) were suggestive for urinary infection that have spread to epididymis and testicle.
Epididymitis and orchitis share almost same symptoms.
It takes two to three days after antibiotic treatment to notice some improvement, but, for complete resolution of symptoms takes longer.
Pain due to acute orchitis can persist for 3 months