Probably allergies, as the first post suggests. That was my immediate thought. You could try an allergy med that contains a decongestant.
The other possibility is ear wax build-up - if a large chunk is blocking your eardrum, you could feel very full and blocked. If you hearing is affected, that could be it. You can try an ear wax softener but that takes a few days to work. There are ear cones that help to soften ear wax as well - available at health food stores. Don't get the kind with a heavy wax coating. You need to know how to use them and you need a helper.
A third option of course is to go to your primary care physician and have someone take a look in there - they can tell if there is fluid behind the ear drum, redness in the ear canal or around the Eustachian tubes. They can see if there's wax buildup and they can wash it out with a special device and a squirter full of water - I've had it done several times and it only takes about 20 seconds and is not painful. I did not need an ENT - just my internist or physician assistant.
Good luck.