I've had dandruff for 2 years now?

Since dandruff is produced by an overproduction of sebum (skin oils), it would probably be a bad idea to wash with a medicated shampoo daily. It would more than likely exacerbate the problem by drying the scalp too much, prompting your body to produce MORE sebum. Try a once or twice a week wash with a product containing tea tree oil, or try rinsing your hair with apple cider vinegar (it doesn't smell when dry) then with cool water. I doubt there's anything you can do at home to make it go away permanently, so it's just a maintenance thing.