I also agree it depends what kind of person you are, how objective and realistic. I think the trouble is that people have too personal a slant on things, can think it's worse than it is (objectively medically, in the grand scheme of things) and I imagine have a tendency to add in things which they wouldn't have normally have thought to mention just because they see certain words on a page, the mind is a powerful thing.
I think there is also the drive to be diagnosed with something, to have a name and a treatment almost as a validation if that makes sense.
I find the internet a great tool for looking up details on conditions I've been diagnosed with, medications, support groups and information, all kinds of things. I do know some hypochondriacs thought and in their hands the web can be a dangerous thing!
I don't expect to go to a GP, tell them a few symptoms and expect them to make a diagnosis then and there and walk out with a treatment. Yes, of course, sometimes it's possible with more common or obvious symptoms but I appreciate my GP has to look stuff up and needs tests and sometimes just time to see how things go, similar with specialists. It can be frustrating but it's just how things are sometimes.
Em, if you think things are related to your fibromyalgia then I don't see how an MRI scan would help either. I have fibro which my rheumatologist manages alongside my rheumatoid arthritis. I've never had an MRI scan suggested for it. I've had 5 for various things (arthritis, bowel condition and Meniere's Disease), but never for the fibro.
Do you see a specialist and are you on any medication or other therapy for it? Could you not give the scan a try? I'm not keen on a lot of the stuff they've done to me over the years but it's been a necessary evil to help them see whatever they've needed to.