Hi, I've Always Been Pretty Clean With My Hair And

Hi, I've always been pretty clean with my hair and I've always used the right shampoos and conditioners to take care of my hair. But, recently, maybe 3 years I've been noticing white stuff on my scalp, at first I thought it might've been dandruff however I've tired every dandruff shampoo in the market and even natural remedies for dandruff but I still see the white stuff on my scalp. It's even when I wash my hair I get it stuck in between my fingernails, or even when I scratch my scalp a little. It's really gross, and it feels like buildup greasy dandruff.. I don't know what to do, it's really embarrassing.. Could you give me some advice on how to treat my problem? Thank you.