There are indeed people with sensitive scalp. And, as you know, shampoos from the nearest supermarket contain aggressive detergents that disrupt the natural pH balance of the skin.
When I had atopic dermatitis, I used drugstore brands. Bioderma Node shampoo worked well for me. It contains no aggressive laureth sulfate, but it contains lactic acid, which softens the scalp. There are, of course, cheaper analogs.
The only strange thing is: why didn't your dermatologist advise you on the best shampoo for you to help solve the problem? Maybe you really need to change your doctor first.
you can try to change not the shampoo, but the dermatologist. Well, to make sure that almost all shampoos really do not suit you, and not the doctor overlooked something
Recently I ran into this problem - all the time I thought that I had dandruff, but it turned out - psoriasis, the lotion for psoriasis helped (ask at the pharmacy), try rubbing it into the scalp after a shower, it helped me on the third day, dandruff no, I'm not suffering. And at one time I also tried a lot of shampoos, including medicinal ones.