Help! My scalp is itchy and oily. It's flaky too, but not terribly so.

I suspect I might be reacting to shampoo chemicals, but then wouldn't it be worse on Day 1 after a wash? It's worse on Day 2, and I rarely make it to Day 3. It certainly looks greasy and gross on Day 3. I could never leave the house on a Day 3.

I have some Loprox shampoo that my dermatologist prescribed when I was in his office for something else (Get those black moles looked at, everyone!) It works really well for Day 1, but Day 2 is no different than any other shampoo.

I have used 100% natural shampoos. I've tried 2 or 3 varieties of Aubrey Organics, and I really like their 'Calaguala Fern', but I'm still itchy and greasy on Day 2.

My goal is to only wash my hair twice a week because I know water is damaging, and besides my hair doesn't seem to need conditioning as often as I do it. It's my scalp that's so demanding!

Suggestions? Comments? Interpretive dance?