hello and welcome to health care magic,
As you correctly opined you may have a sinus
or a Eustachian tube problem.
In any case get an audiometry
assessment including PTA and Impedance and also a CT of the PNS and get back to me or any ENT with the reports as soon as possible.
Meanwhile try steam inhalation with menthol or other vaporiser and do not get exposed to loud noise and also give a detailed report of any medications that you are taking presently.
Dr Sriram nathan