I've a few ideas that come to mind. I believe that an ENTS (Ear Nose and Throat Specialist) should be consulted. If it is pressure problem there are simple fixes a few of which I am aware of out of my own experience.

Perhaps the problem is a difference in pressure between the inner and outer ear. This could be caused by blockage. It could be caused by too narrow and/or blocked eustation tubes (my problem). Removal of adnoids can be a fix. The insertion (simple procedure) of small tubes in the eardrum is another possible solution.