What Causes Armpit And Vaginal Area To Be Darker In Color?

Hi i m 17yrs old girl indian. I m fair but my armpits and vaginal area are dark brown in colour. I m not sexually active. Even my inner thighs(near vagina) are dark n have blackheads. Please help me what should i do to make them white. And also inner vaginal area is a bit pink n rest is dark! Please suggest some lotion or medicine!