Welcome to healthcare magic
Read your history, It could be hand foot and mouth disease. It is a viral infection and therefore you can have malaise
and muscle aches as well. Only thing is you don't seem to have mouth ulcers which is very common in HFMD. Lesions are usually seen over hands and feet, but buttocks can also be involved. Again thighs, neck and arm is not usual but possible. Did your doctor rule out Chicken Pox
. Chicken pox vesicles will have an umbilicated centre (depressed).
It is better to take a dermatologist's opinion. Drink plenty of fluids, take rest and take antipyretics like paracetamol
Hope this helped.