My dog has fleas and I've done many things to treat him but nothing has helped. I don't have a lot of $. HELP!?

I've bought Hartz flea shampoo and given him baths. I bought Sentry Pro flea drop and applied it to the back of his neck as instructed. My dog is a 19 pound Jack Russel. He won't stop whining and his skin is starting to scab from his biting/itching. I don't have a lot of money to take him to a Vet but please any suggestions help!