I have a 16 week old kitten. Yesterday I took him to the vet as he was shaking his head occasionally and I could see black wax in his ears. The vet nurse examined his ears with a torch thingy and cleaned them with cotton buds. She looked at the residue under a microscope and said there was no sign of mites. He was due a flea treatment so he had one which she said would also treat mites however today he is shaking his head more than ever. Should I take him back to the vet!