What Causes Irritation At The Tip Of Penis?

i recently went to my dr. due to discomfort at the tip of my penis where my urethra is. it does not hurt to pee or have an orgasm. I also do not have any dis-colored discharge. if i m wearing lighter clothing like gym shorts, it doesn t bother me as much, however if I where jeans, it seems to irritate much more. any thoughts?