Hi, MC, and welcome! Yes, Donna is correct. Lightheadedness is a symptom of fibro but also a symptom of other illnesses. I will get a "wave" of lightheadedness out of nowhere...to the point I need to sit down or I think I'll faint. It goes away just as fast. It looks like you have been having tests run to rule out other illnesses. Many use a rheumatologist for their fibro. I use a board certified Internist.
Be sure to check out the Fibro 101 thread...the second thread on the forum. There are links to good info about fibromyalgia, including a list of symptoms. You just might "see" yourself there.
Keep searching for answers. You do need a diagnosis but you also need a doctor that believes in fibromyalgia and will help you. That is very important.
I am so glad you found us, though, and joined in. We have a good group of people that love to help one another and, as a bonus, we really do care about each other too. So, read Fibro 101, back posts, and ask questions. We are here to help you. Hope to hear more from you soon.
Sherrine