Suggest Treatment For Dandruff Problem

Hi my name is Alicia lew and I've had dandruff for 3 years now. I have a healthy diet and I drink water most often. I exercise frequently and I've tried Many anti dandruff shampoos such as head and shoulders , selsun blue , nizoral , and tea tree shampoo but nothing is working. Do you have any suggestions for me? My email is YYYY@YYYY