What Causes White, Dry Spots On Head?

Hi doc. . .in my childho0d i got these dry white spots on my head tht looked like ''dandruff patches''.i am aged 21 now and after using all different types of shampoo's and creams a physician gave me i have noticed that these patches has turned red and is sore at times. . .it even thinned my hair out and im going bald now. . . .please please please help me. . .