I'm not a doctor, but I know there are Many possible things it could be or contributing factors
Certain STD's, Allergic Reaction to a substance, Jock itch if your feeling an itch and perhaps even a yeast infection, with or without obvious symptoms or appearance in my case, I've also had similar problems especially the itching which has led me to believe that mine is a possible yeast infection, you may have to change your diet if your eating or drinking junk food too, which is better for you anyways, my suggestion is go get checked by a doctor and start ruling out things so you can narrow it down, also if your sexually active with more than one partner or they are and not protected, all parties should get checked.
One: Have you been tested for STD's, if not and your sexually active, it's highly recommended so you can rule that out or find the cause
Two: If you feel it may be your prostate, you should get that checked too, could be possible Prostatitis as well, if that's the case then you may require antibiotics
Three: Stay clean and keep good personal hygiene, don't let that area build up moisture either cause bacteria will thrive on it, keep it dry, wear loose clothing when possible and cotton underwear, drink lots of water, at least 8 bottles a day to flush out system, depending on what it is I suggest adjusting your diet and lifestyle accordingly.
My thread and if it is a yeast infection, you can read what I did at the bottom, it may help