Ok, I am a chick but I was the "unlicensed doctor" to my friends back when we were all broke in college and had no medical insurance so I have seen a few things. (Btw I do have a medical background, I am not an actual doc though). Ok, so since you are uncircumcised there is a pretty good chance it is a yeast infection. Yes, guys can get them too. Does it itch at all? If yes, then probably yeast. Get an otc creme like Monistat or Vagisil...you can claim you are buying it for your girlfriend if that helps. Slather it on every day for a week and the problem should be solved.
No itching? Hmmm... This doesn't sound like an std but you might want to review your safe sex practices and check with your partner(s). If nothing seems to fit the description then I would give a urologist a call...it is probably something minor but they will have more experience diagnosing such things.
Hang in there!