How do I fix my dandruff?

Alright so i started getting dandruff last december. It wasnt that bad but its slowly progressing to now im losing a decent amount of hair when i shower and everytime i run my hands through my hair then usaual. I tried nizoral and used it for 3 weeks 2 times a week but its not working. My scalp is super itchy and dry but my hair is like oily. I dont know how to fix this any ideas?