It could be. You really need to go see a Gyno doctor...DO NOT WAIT ANY LONGER. If it is an STD it sounds like a curable one. But dont wait till it gets worse.
Don't mean to scare you, but I have the same thing. Except I know I have HPV (Genital Warts). They are extremely common, however, very hard to get rid of. Read my message above which might help explain a bit more.
I hope for your sake that it isn't.