I have been experiencing mild irritation from my urinary tract. As of today I am seeing a white discharge?

coming from my penis. I feel no pain when I urinate. My urine streams to the right as opposed to straight ahead. I assumed it was an STD so I went and got tested. The culture came back negetive for Chlamydia and Gonorrhea. The nurse told me to go see a Urologist. If its not an STD what could it be? I repeat the culture came back negative for STDs.