I'd only be guessing but some of your symptoms could be caused by a thyroid disorder or even a parathyroid disorder. It's wise to check that out, it may or may not be the reason for your ill health.
Sometimes diagnosing Lupus is a process of elimination, it likes to mimic things and those 'things' have to be either proven or disproven before they move on to the next step.
I hope your appointment goes well. Did you ever find out exactly which tests your GP ran on you that said you were 'negative' - sometimes GP's aren't that up on all the testing for Lupus.
Good luck and let us know how you get along ok?