You need to get a scan of your nose & paranasal sinuses( including both mastoids in the field) direct coronal view, plain films, 1mm cuts. This will show Ears, Nose and Throat in one complete scan. I am suspecting a Chronic Sinusitis which is leading to Eustachian Tube dysfunction to be causing your problem.
Next Steps
Meet your ENT Specialist and discuss this possibility with him.