A properly collected urine specimen showing three-digit-WBC is highly indicative of infection. A urologist is the preferred choice if this is the only abnormal finding.
Three-month antibiotics for chronic prostatitis is appropriate but it takes much longer for the condition to subside completely even in the best case scenario because relapses are part of its natural history. Do consider sticking to a urologist you trust. He / she will be able to patiently guide you out of the woods.