Yep, totally common to have hair follicles up the shaft of your penis. Also common to itch there, alot sometimes depending on the time of year, sweating etc. And you're right, can't be an STD and although there are a couple that pass from parents to their newborns...it is rare and then mainly HIV. I'd suggest using a bit of powder after each shower or change of clothes, GoldBond anti itch works well. Helps keep things dry and prevents some itching there. Good luck!