Tamsin, you have chased this for a good part of a year now and all the docs seem to be saying the same thing. At some point you need to either accept nothing is wrong that warrants so much worry in your life or you need to find completely different doctors till you run out of choices. You acknowledge you think smoking cessation is what you need to do but you don't stop. I'm not sure what everyone else will be able to do for you at this point. Have you considered antidepressants or antianxiety meds? It's time to try something different. Even worrying without a serious health problem this long will stress the body beyond belief. Having a serious health problem and letting it just progress isn't good either. You've come up with quite a few diagnoses from Dr. Google but I'm not sure anyone here can tell you as much as a trained doctor can. I feel for you as worrying about health issues is very tough. Good luck and keep on searching till you get your answer.