Itching like crazy!

Doser has been itching and biting like crazy! We brought him to the vet and did a skin scraping did not find any mites. All the Vet was able to tell us is that he had a skin bacteria infection and gave us clyndamicin as an antibiotic for 3 weeks. It didnt help very much. We have read online about clorahexadine in shampoo that we have found a low percentage of in an over the counter shampoo that has helped alot  with bumps all over his skin but he still itches! Any idea of what else we can try besides a different vet? Any advice we can get is helpful!! It breaks my heart to see him so uncomfortable!!

Thanks!