Extremely itchy hair and flaky scalp

Hello, I was wondering if anyone here can help me with my major hair problem.
My entire head is covered with large flakes (about the size of a finger nail) and I have yet to see any shampoos work for me. It's also extremely itchy even as I am washing my hair. It's like once my hair dries the the flakes are already formed on my scalp. It's disturbingly disgusting.
I heard of using oils but I don't want oilier hair than I already have so it needs to be something else. Tweet