Does your scalp itch? If so, it sounds like you're suffering from contact dermatitis or seborrheic dermatitis. Some people say Nizoral helps the contact dermatitis, but Nizoral can also cause contact dermatitis. You may also want to try a moisturizing shampoo, but I'm not sure if this will work or not. If it's seborrheic dermatitis, you'll want to use Nizoral or another anti-dandruff shampoo.
However, I wouldn't think the flakes from contact dermatitis would be that large as compared to seborrheic dermatitis (or what most people think of as dandruff). which actually induces the flakes. I guess if you're scratching your head a lot, you may induce large flakes to appear in your hair and shoulders.