It seems that probably you may be having tinea versicolor
It is superficial fungal infection
It is caused by melassezia furfur.
It is harmless condition remains unchanged if not treated.
The yeast remains on scalp.
And disease spreads gradually from face to chest,abdomen, arms and back.
The treatment is perfect and simple.
However, for firm diagnosis you should consult dermatologist
Antifungal tablets,cream and shampoo containing ketoconazole
might improve the disease.
The given answer might be helpful to you.
Dr. Ilyas Patel MD