Herpes!?

Every few months I experience a very mild irritation in my vaginal area. Most of the time if I look with a mirror I may see that my labia is red or irritated. I was tested for herpes years ago when I had my first "outbreak", my doctor told me I tested negative for herpes but never went into detail about what it was. Does anybody have any idea what this may be related to? Only information I can give is that normally, when it happens, I go off my period just days before. Could I be having a reaction from the tampons I use? If so, how come it only happens, sometimes?