Even if there is no fluid in the ear showing a normal Impedence audiometry, ear pressure on lying down is most probably due to Eustachian tube dysfunction which correlates to the inflammation you have in your sinuses, while your ear examination with PTA is normal.
Next Steps
I suggest you do a diagnostic nasal endoscopy to check for the eustachian tube function. Continue with the treatment prescribed to you. We can add antihistamines and nasal decongestant sprays followed by steam inhalation.
Health Tips
Consult for further details of management.