What Causes Persistent Popping Sensation In Ear Of A Child?

My son is 9 and he says his ears keep popping, like when he swallows and everything gets really loud, his voice sounds kind of muffled (to himself) and all other sounds are really loud. He takes his finger under his nose and sucks air in to pop his ears back so everything is not so loud. He says it doesn t hurt, but he gets very frustrated. He has allergies and sometimes gets headaches, he had one last night and had a fever, I think he may be clogged up so it gets worse he he has allergies bothering him. He has had to do it more in the past few hours, but I notice him doing it quite often...