Specialists do get it wrong. Was he a consultant or a trainee? Alternatively you may have two problems but your story is very suggestive of otitis media aka glue ear aka fluid behind the eardrum
Moreover if you have had a general anaesthetic for your back this may well have produced glue ear - an ENT surgeon may not know this!!
Call the hospital, speak to the specialist's secretary and ask for either another consultation or a second opinion. Without waiting. If you are in the UK and are stone walled ring the chief executive's secretary and ask to make a 'formal complaint '
Sorry to have to advise this but it does work. I suspect once you get to see a specialist face to face and tell them this history and the fact you had a back operation they will look in your ear again and may find some fluid
Even if they do not you can then be reassured nothing has been missed