What Leads To Vaginal Itching And Dark Brown Discharge Between Menses?

i have this vaginal itching for quite a long time.. i went to the OB twice, and had taken oral meds plus vaginal creams.. However, the itching is still present. Not often, but once in a while.. I also notice that I have dark brown discharge between my period. What might be the problem? I am not sexually active. I am 19. is this serious?