THere are MULTIPLE possible causes for this pain. A kidney stone (or rather kidney gravel, a number of very small stones) could be the cause. Recent alcohol consumption by history is consistant with this. A bladder infection of some kind is another possibility, as is a prostate infection. The only way to really know would be medical tests when you are getting the pain.
Feel free to ask a follow-up question.
ANd a BONUS is always appreciated.
Two days would be early to show signs of an STD but not impossible. Even more reason why testing is needed!
And a BONUS is always appreciated.