Itching in the urethra, sometimes white discharge appears from the urethral opening. What is this?

Patient's question:

Age
Medical history: Had nephritis at 15 years old
Since then, there has been a history of intermittent difficulty urinating, a sense of fullness in the lower abdomen when holding urine, frequent urination, and occasional urinary urgency. There has been no morning erection or nocturnal emission. Believes oneself to have prostatitis but has never been tested.
In the past 3 days, there has been urethral itching (sometimes itchy, sometimes not itchy), and sometimes white discharge from the urethral orifice has appeared. Recently had sexual relations with a girlfriend. What could be the cause?

Doctor's answer:

Hello: You should go to the hospital for a secretion test to see what type of bacterial infection it is.