I know exactly how you're feeling. Although the ENT told me I had no inflammation when I was scoped (a little over a month now), now that the burning throat is back, I am also scared it's cancer. The ENT scope only looked as far down as the upper sphincter. Anything lower requires a Gastroscopy...which I'm scheduled for in February!! That's 6 months away! I don't think I can wait that long and will be looking into alternatives come Monday.
Although I do not know a lot about throat cancers, I have heard it's quite aggressive and if you've had burning throat for 3 years, I think it may be safe to assume that it's not...
Have you had a Gastroscopy/Endoscopy done?