Please save your money for a consult with a vet, or apply for Care Credit. Care Credit is a low to no interest credit card that can only be used for medical, dental or veterinary bill. In the mean time please apply topical flea and tick preventative every 28 days since not seeing a flea does not mean that your dog has not been bitten by one. Dogs with flea allergy dermatitis can react, by itching, to a single flea bite for a month or more. Other types of itching problems can be caused by mange (scabies, demodex and others), autoimmune diseases, skin allergies, fly bites and more.
Not a doc, and you posted here for a vet sorry... but, wanted to suggest to you to read up on low thyroid. Check your dogs nails and if they look brittle, or/ and the hair is thin, really consider this. It also might just be flea allergy. My dog gets the flea bumps on him when his thyroid is low- that is why I wanted to point that out to you.
I have a golden retrever ythat has same problum an i find that oatmel shampoo an supliments have helped a great deal. avoid medicated shomppos as the tend too dry the skin out..