What are some reasons that my right ear frequently feels like it has air trapped inside and it pops?

Eustacion tube. This may be related to eustacian tube dysfunction. This a tube between the inner ear and the nasopharynx. Its' purpose is to relieve air pressure that builds behind the ear drum. Pressure may build and suddenly relieved with a yawn or other maneuver that pulls the tube open.
Eustachian Tube prob. You more that likely have a poorly functioning eustachian tube. This is a tube from the back of the throat to the middle ear that equalizes pressure in the middle ear. If you cannot clear your ear with blowing against the pinched nose and it recurrs, you more than likely have this. Allergies, colds, tumors, thyroid disease and many other things contribute to this. See ENT doctor if continues.