It could be glue ear, alot of GP's don't seem to find glue ear, not sure why.
My DS2 had it and the ENT picked it up within seconds of looking, the GP didn't see it all!
The ENT put grommets in the first time and DS2 was fine after that, he did have a repeat of the grommets and also his adenoids removed to help with drainage. It apparently quite common for boys in particular to have small ear canals when young.
I would be ringing the ENT to try and get an earlier appointment.
I had to ring our ENT everyday , after a week, I fluked a cancellation.