inside vagina itching

Hi I have a question I hope someone can answer: the inside of my vagina is itching, really badly, for 2 days now and I looked to try to see where it was and it is the labia minora and the opening of the vagina. today i was uncomfortable and itching all day and when I Got back from school and went to pee, I noted the swelling of the opening of my vagina. it sticks out when I close my legs. what is happening? I had sexual intercourse one month ago with my "sexual partner", he is clean and he just had sex with 2 ex's, which were virgins when had sex with him. and actually talking to him the last time, he told me the reason why he didn't have random sex like the majority of guys in our school because he is freaked out and scared by STD's. Previous to having sex with him I had sex a year ago with my ex, and I never had problems of any type. I am on the patch and the cycle ends today, so I should be getting my period by thursday. Why is the swelling and itching?
thanks!