Hello,
It is time to call your vet and ask for help. Itching can have a huge multitude of causes and there is not one answer to every cause. I would start at the vets office and look for the easy things like fleas. But it could be allergies, infections, disease, mange, etc etc. it is a long list. The sooner you get to the vet the cheaper, quicker and easier your dog will be feeling better. I would strongly recommend you start at the vets. It’s much cheaper in the long run