I know what you mean, I've been really struggling to believe there's nothing more serious wrong with me. It can't be a tumour, they don't behave like that apparently. It really does seem like anxiety or maybe just your sinuses or something. Worth going back to the doc - even if it's to get referral to someone about stress, maybe?

If you're lucky enough to have private healthcare insurance (assuming you're in the UK), then there are plenty of people you can see to make it better really easily, though you can see them all on the NHS too, but might need a bit more persuasion at the GP!