How do pilots cope with pressurization changes? I have tried 


drinking a glass of water
yawning
plugging my nostrils and pushing air


but none of these seem to work - I still have a distinct pain in my upper sinus cavities when changing pressure in an airplane. I have the same pain underwater. 

Do some pilots have this problem, and do they have a remedy?
There is a chance you suffer from aerosinusitis but you should consult a physician to obtain a proper diagnosis (Disclaimer: I am NOT a doctor). For what its worth commercial planes are pressurized generally to about the pressure you would see at 8000 ft. this equates to about .75 Atm. In the reverse case 33ft underwater already has you at 2 Atm.

When I fly (generally unpressurized) I usually chew gum which i find helps.