Your story isn't giggle provoking.
Even though it's real and it's happening to you, having your anxiety written in your file, will follow you from now on.
I am not first hand experienced person of your troubles, but went through all this with my son.
Popping, you mentioning in your neck, he had when he was small child. We went through so many emergency visits and scanning, and nothing dr(s) found.
Slowly but surely, my son forgot about it and almost I did, too.
Then his late childhood and early adolescence came and his anxiety/panic got diagnosed.
Unbeliveably, his family doctor didn't want him in anymore for anything. Since he became: mental health department patient.
His psychiatrist never wanted to talk of getting of the psycho meds. Only option she gave was: to either increase med(s), or add some more. Unfortunately, his psychologist decided to decline my son's visits with Insurance (HMO), because there was no visible change on horizon in his way of thinking. So, psychologist said: he didn't want to waste neither his time nor our copay money, since our son (21 then) wasn't going to change his way of thinking. Our son, on the other hand was saying: "this is who I am, I can't change of who I am".
And so his visits stopped; he gradually took himself of all the meds and started tiny bit by tiny bit, accepting of who he is: not special but umique.
My suggestion would be: keep visiting your new doctors, so change them until you feel comfortable with one. See if possibly they will approve of MRI on that neck/head area.
Don't let them bring on anxiety in picture of that "newly" realized trouble of yours.
But, only you can put the end on when to stop asking for new and new tests.
Just last summer, my son kept going for some somatic isuues (to all brand new primary) and wasn't ever going to be satisfied with results. Until:? he was suggested surgical diagnosis. Guess, what? That hurts as hell, and he decided to stop bugging doctor, and slowly he forgot about his problem.
This was enough to prove that his anxiety was playing tremendous role in all the new somatic uncommonness he was convinced he had.
So, maybe, I say: maybe only, your existing annoying neck symptoms might metamorphosize, if dr(s), for example, say: they need to do surgcal diagnsosis on your neck portion of spine.
Based, on myself watching our sons "life catastrophe", I am hoping that you, too, are fine.
But, I don't know anything. Doctors do. And to them, you only, should trust.