Based on your description, it appears that you have facial melanosis which could be compounded by acanthosis nigricans. These conditions have a strong relation to one's internal health and it needs to be evaluated as often quoted - Skin is the mirror of internal health. Attempting treatment without understanding the pathology will be futile and make the course longer. Your dermatologist will decide a treatment plan for you after a consultation. Internal health needs to be fixed based on blood chemistry reports. Apart from active pharmaceutical medicines, a healthy diet and lifestyle is mandatory to achieve results.