Hi there - have you seen an actual consultant (extremely preferable) or a registrar (useless in the extreme).?
Any other symptoms - tonsilitis - fever at all?
Push for a scan of some sort.
It could be a general infection of some sort which would respond to a powerful antibiotic prescription. I had one just recently - I was very worried (thought i might have had a recurrence) - antibiotics cleared up a tooth type infection.
But you must keep pushing so you get your peace of mind.
Hope it all works out well for you