My dog keeps getting infections in her ear and her feet the vet says its her food but i dont belive it is?

Ever since my dogs been like 4 months old shes gotten really bad ear infections and feet infections the vet sayd its a yeast infection the meds fixs it and it comes right back. Now shes two and its to the point where she eats her pads off her feet and limps and her ears are all black inside i changed vets and they said they thinks its a food alergy so she is on special food and alergy meds its been a month now and it doesnt change it goes and comes back like it has for two years. I dont no what to do i cant afford to keep taking her to the vet only to be told the same thing. I realy really belive its not a food allergy has anyone elses dog done this? She breaks out in bumps sometimes too, pukes on accasion, wont everrrr stop licking at her feet an biting them im constantly telling her to stop, her feet get really fat and red and swollen andup in the web of them gets black and pussiey, she eats her pads till there gone and bleeding, her chins red and she itches it everywhere, the folds of her mouth get the same yucky black stuff her feet and ears get, she licks at her vaginal and anal area constantly, she itches her ears so bad her hair goes behind her ear and gets bad gouges, her ears are red inflamed and have black stuff and she occasionally looses her fur on her back. This happens year round doesnt change with season or weather shes on the most hyperallergenic dog food there is and now shes bein given steroids nothing helps ever. Any suggestions?