What can I do about rapid hair loss and dandruff?

I'm 14, ud shiny, healthy hair. Se puberty severe dandruff jt wouldn't regardless shampoo medication tried. Wh dandruff greasy hair slight hair loss, wasn't bad. dandruff greasiness away, rate hair loss increased rapidly.

I sl look OK hair qe thick, at hair bedroom floor ry scary. Wt brought sudden hair loss? it?