A blocked eustacian tube, otherwise known as otitis media or 'glue ear' is very common and I doubt an ENT specialist will be stuck by it (forgive the pun). Decongestants work in some, and usually the problem is seen in children and improves at puberty, but if this doesnt apply in your case, the answer is grommets. This is the most minor of operations and can be done under local anaesthesia, although I would recommend general anaesthesia. Far from damaging your hearing, it will improve it. Leaving things as they are is not just a career problem - chronic otitis media can permanently damage your hearing.
I suggest you sit down with those ENT chappies and ask them to spell out the benefits and risks, get your grommets in, and carry on flying