If he can't get secretions, he should check your urine afterwards for white blood cells. Even if he doesn't see white blood cells, you still could have an infection. Telling you that you have benign prostate enlargement means that you have an incurable condition that is treated with muscle relaxants and drugs to block derivatives of male hormones, that cure nothing and help relieve symptoms only a little. Your best bet is to take antibiotics for several months. Most urologists do not order semen cultures because they claim that they are always contaminated with germs from the skin.
Most men collect semen cultures from the vagina or mouth which always is contaminated.
If the patient is asked to shower and clean himself with soap and water, then collect the specimen with his hands and then let it squirt into the culture jar without touching it, the culture is very dependable. Prostate infections are extraordinarily difficult to cure because antibiotics do not accumulate in high concentrations in the prostate. So most men have to take appropriate antibiotics for many months and their partners have to take the same antibiotics for a much shorter duration. I often prescribe a combination of Cipro and doxycycline for several months. If you do not feel much better by six weeks, you may need to ejaculate frequently or find a kind urologist who will agree to massage your prostate at least once a week while you take the antibiotics.