First, I want to say that it makes me so angry when doctors get their patients all worked up before they get the results of the tests that they gave. It has happened to me many times.
I understand everything you are saying and feeling. Of course you don't want to die, I think we all think about it, but inside, we want to be able to live our lives to the fullest. Here is what I try and do. Worst case, say it is Lupus. You can finally breath and be assured that you know what is wrong, and finally start doing all the things you need to do. Try and look at it as a blessing not a diagnosis.
You will be in my prayers for the best outcome!