Have you tried any prescription drugs, such as flomax or any of the over-the-counter drugs to help with burning when urinating? Or drinking 100% pomegranate or cranberry juice. Given that all the tests are negative, it would seem like there's some help in your future. Maybe some new doctors for their take?

it doesn't burn when urinating - the pain is in the penis and disappears for a while after being able to dribble a few drops - flomax doesn't help against the pain