Burning stinging on scratching is usually a sign of very dry skin. Applying a good moisturizer and using moisturizing body soaps would help take care of this problem. In dermographism, usually you would have wheal and urticaria like symptoms with raised skin patches and intense itching. So, this appears to be unlikely but then only a skin specialist or doctor who can examine you after you scratch your skin can tell for sure. Apply a good moisturizer, eat healthy (plenty of fruits and green veggies) and drink water, fresh juice, clear soups etc and see if it helps. If it does not help, you will need to consult a doctor. Take care!
The medical advice given should not be considered a substitute for medical care provided by a doctor who can examine you. The advice may not be completely correct for you as the doctor cannot examine you and does not know your complete medical history. Hence this reply to your post should only be considered as a guiding line and you must consult your doctor at the earliest for your medical problem.