Then I would suggest a change of GP if possible. Do some research on all the possible causes of tinnitus and see which seem to apply to you, then go armed with that information and refuse to take no for a answer. I wish I could be more productive in your efforts, but exhaust every avenue before you give up completely. What noise colours have you tried? Have you tried any other sounds, like whales talking, or nature sounds? Sometimes they can help if you are able to find something that is around the same pitch.
I dont know enough about hyperacusis because I have never heard the term. I know it effects my left ear, a constant hum below the ringing, but right ear is ok, just ringing. It does seem a rare morph of tinnitus. What can be done about that, I have no idea, but intend to read more about later on.