Hi im 18 and i have had a long term girlfriend for 2years now she is my first sexual partner, recentley I keep getting really itchy testicles and around my anus, i also get a rash aswell, it also gets worse when i have had sex. i have been putting sudocream on it and when i get out the shower i put baby powder on to stop sweating, but this hasnt seem to stop it as it comes and goes?? my girlfriend doesnt have any problems after sex. could it be a STI? What is the rash and itching and how can i get rid of it? thankyou x