healthy scalp & getting rid of dandruff

I have a problem with dandruff building up on my scalp. When I look through my hair at my scalp I can spot big flakes and when I scrape them off it leaves a red mark. I don't mean to be gross, but I'm concened it might be causing my hair to thin and making my hair grow slow and be unhealthy from an unhealthy scalp. I thought it was just a dry scalp and was using monoi oil, jojoba and olive oil on it but it didn't help. I take a teaspoon each of of flax seed and cod liver oil. I've switched products around from drug store brands (i.e. Clairol, Aussie, etc) , Paul Mitchell, Aubery Organics, Abba, and the list goes on thinking maybe an ingredient was drying/irritating my scalp's skin. Any other ideas what can be causing this? I don't have the money to go to a dermatologist for this so just trying home remedies.