Hi,
Welcome to ehealthforum.
It is difficult to comment on the cause for the symptoms that you describe (hyperpigmentation, dryness and itching) without examining you. Consider visiting your doctor/dermatologist for thorough evaluation and assistance. Chances of infection, eczema, frictional hyperpigmentation should be ruled out. Discuss about option of skin lightening treatments to help you. Proceed with further management as instructed.
Take care.