Why does my dog smell this bad?

i gave my dog a bath 2 days ago. he smells very bad now and doesn't dig or play with old smelly toys. its not his body but its coming from his head. when he was a puppy he always had a bad ear infection in his right ear and took 8 weeks to treat by the vets medication. we always clean his ears during his regular grooming when we brush his teeth and for some reason his right ear smells again. i looked with a flashlight and there is nothing in there or any signs or infection of wax build up because we are very though with his ears because of his history with infections. what could this be and how could i prevent it from getting worse and possibly treating it without going to the vet?