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

Patient's question:

Age
Medical history: Had nephritis at the age of 15
Since then, I have been experiencing: difficulty urinating, a feeling of fullness in the lower abdomen when holding urine, frequent urination, and occasionally a sense of urgency. I have never had morning erections or nocturnal emissions. I suspect I have prostatitis but have never been tested.
For the past 3 days, I have noticed itching in the urethra (sometimes itchy, sometimes not), and occasionally white discharge from the urethral opening. I recently had sexual intercourse with my girlfriend. What could be the cause?

Doctor's answer:

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