Thanks for using HCM
From what you described, the dark vaginal parts (vulva i assumed) is something that has been there for a long time. If that's the case, the most likely causes could be chronic irritation from some under wears(hypersensitivity
reaction) and dermatomycosis such as that cause by candida species. The severe itching
and burning urination are typical of a candida vulvovaginitis which could be accompanied by painful sexual intercourse and vaginal discharge
which is adherent, thick and of little or moderate abondance. Another possible cause of the severe itching could be an infection with Trichomonas vaginalis
is sexually transmissible.
You will need to get a doctor to do a proper examination and eventually priscribe anti fungal drugs (tablet or ovules and cream) such as fluconazole
Hope i did help