yellow discharge from my urethra- prostatitis or chlamydia?

I have only ever had sex with women using condoms, i haven't had sex for almost a year now. I haven't masturbated in like 3 days, i haven't had a shower today. Anyway, the problem is a smelly sort of yellow discharge from my urethra. There is also some pain at the tip of my penis. Also i study microbiology, and the smell of the discharge is not too different to the horrible smells that come from the nutrient agar plate of things such as C. sporogenes, or maybe M. luteus or something.