The scalp health disorder you experience is dandruff, is a dry and white scalp, which often causes itching and ultimately causes self-distrust for the sufferer.
Here are some things that can cause dandruff, which are: have dry scalp, Malassezia fungal infections, rarely shampoo, seborrheic dermatitis, hair allergy products specific, psychological stress, lack of nutrients such as vitamin B / fat / zinc, or heat.
Since all the shampoos to get rid of dandruff have been tried and the results do not show improvement, the best solution is to see a dermatologist, and discuss this issue, so you can do a further series of further tests, so that ultimately proper treatment can be given according to the exact cause that causes your dandruff.