Muffled Hearing In Ear and Odd Feeling In Ear as Well As Popping (Sorry about Double Posting)

My son has muffled hearing in his left ear. He can't hear very well in it at all. It is starting to effect his right ear as well, though only slightly. His left ear occasionally pops when he swallows, and he claims that it usually feels like something is in it, or like it has popped and has yet un-popped. He has tried plugging his nose and trying to exhale, but it hasn't helped.

I took him to the doctors and they cleaned out his ear, but it didn't help, and he is currently lined up for a hearing test on MARCH 30th! Can you believe that, a serious problem, and they schedule him for over a month away.

I am strictly talking about when he has a certain ear plugged by his finger. It is very odd though. He can hear fine when neither of his ears are plugged, and we first noticed this when he plugged his right ear and tried to talk, which made him realize that he has muffled hearing in his left ear.

He is 14, if age has any effect, and listens to loud music, but I doubt this could be the problem.

Please help!
My son is terrified about losing his hearing.