Yeah, MS comes up a lot on most of the searches we so poorly choose to do! I have had MS fears for years, as have, I would imagine, probably most everyone who has an anxiety issue.
My grandfather actually has MS, so it adds a little more anxiety in my corner, BUT he is also almost 90 years old and considering, quite healthy. Has had MS for probably 2 decades or more now. Sure he has some issues like balance, and needing a cane and emotional inconsistency but other than that, he is doing fairly well.
Here are a few things you mentioned that are worth noting.
You said "Ive never had any debilitating symptoms though, nor do any symptoms "progress" or get worse. "
MS, while it can be relapsing/recurring, usually is progressive. Remember that. And even in the relapsing/recurring times, it isn't a now I have symptoms and in 2 hours I am fine type of coming and going. Anxiety does that..clearly and very reliably.
You have had the physical neuro tests and all was well, another good sign.
Finally, that feeling you are describing..I get it ALL the time. One of my biggest symptoms, especially in large open areas, large stores, in crowds, etc. It still ***** every time, but I have become accustomed and can generally ignore it, which of course makes it go away. Our anxiety only has the power we allow it to have (though, admittedly trying to disallow it can be hard!).
I also have BPPV "attacks" from time to time and have had them for the past 15 years, so sometimes my issues are related to that as well.
Here is where it most likely comes from. When anxiety raises its head, even subconsciously, there are lots of changes that happen in our bodies. One of which is vision changes, including pupil dilation. There is good reason for this as it relates to the survival mechanism that is being invoked. Balance is reliant upon several systems in our body, but the 2 most important are vision systems and inner ear system. It would then make sense that if your vision is being changed, ever so slightly, that you would feel this weird feeling. This, of course, causes more anxiety, which ramps up the other feelings.
So, do not fret, it sounds like what you are referring to is indeed run of the mill and usual anxiety symptoms. Hope that helps in some way.