How can you cure dry itchy scalp with dandruff?

I’ve had this problem for nearly a year and have tried dandruff shampoos, medicated shampoos and conditioners, tea tree oil hair treatments, lotion, washing my hair more (to get rid of excess oil) and less (to prevent over drying), and quitting blow drying. Nothing seems to work, and as I’ve said, it’s been this bad for nearly a year! Do you guys have any more suggestions? Thanks!