White patches under your foreskin can be many things including a fungal infection or a bacterial infection. Try not to irritate your skin more by examining it frequently and pulling back your foreskin frequently. Follow up on it with your doctor.
Always use a condom for oral sex , anal sex and vaginal sex. They really do significantly cut down on your risk of sexually transmitted infections. The younger you start having sex, the more likely you are to contract a std in general so be smart about it ( you didn't mention if you are using condoms or not - just reminding you to do so ).
www.iwannaknow.org is a terrific website for teens about sex and std's. It's a great site to learn more about since you probably haven't gotten much std education in school at this point ( plus what you do get typically ***** ). Encourage your friends to visit it too -it's ran by asha which is one of the leading std educators in the US.
grace
Did you use a condom? Also 14 is young to be having sex.