Hi,
How old are you?
Differentials for the skin condition will be seborrheic dermatitis, psoriasis , a fungal infection and dermatitis. I do not want to cause unnecessary worrying here. What I have posted are only differentials. These are conditions that may likely explain your symptoms.
Seborrheic dermatitis may present as greasy scales over the scalp, chest and armpits. We commonly refer to these flakes as dandruff. A fungal infection may have well defined borders and may also present with scales and itchiness.
I suggest that you have this evaluated by your physician. Each differentials mentioned above differs slightly in management. But for some conditions like psoriasis further evaluation is needed.