Botton line if you think the urethra discomfort is from a herpes inside it, it is highly unlikely as it would be extremely painful not just a discomfort,
I know when I was tested for a UTI, they said it was negative, but they said they found an infection of some type there, but they couldn't tell what it was because the sample was contaminated.
Hi, pain while urinating could be a caused from a UTI from the oral sex but you wont know unless you see a doctor. you know your body best and if your having urethra discomfort that is not natural to you then do have it checked out and needless worry is a waste on energy.