I would be pleased to answer your question .
From the description it sounds like P versicolor
This is a condition where the body loses tolerance for a yeast called Malassezia
(which is present normally on all our skins) and starts attacking it leading to symptoms. This condition responds fastest to a steroid
and antiyeast lotion applied on the area twice a day. This requires a prescription and your doctor can write one for you. If you cannot see your doctor for any reason then here is what I would recommend trying:
Nizoral-AD shampoo: apply and leave for 5 minutes on the scalp
chest underarm shoulder upper arm uppper back after working up a lather. Do this every alternate day. (e.g Mon-Wed-Fri). Use regularly for 4-6 weeks then start decreasing the frequency of application gradually till you reach once a week and maintain. This shampoo does not require a prescription.
Thanks and take care