I've had constant dizzyness since I can remember. I'm 20 years old right now, i've gone through many of the tests you all mentioned. Was checked for menieres, it was negative, had a ct done, that was negative, I even visited a massage therapist to help, since it seems no else is able to cure this, but it didn't help either.
I've actually just had a dizzy spell an hour ago, which lead to me searching online in hopes to find some info, and eleviate the worry that often accompanies a dizzy spell.
I've had dizzy spells since I was a child, I can remember in school getting an attack where it appeared like the room was spinning, I didn't know how to describe it or what it was as a child, so I sort of just lived with it. It can't be something serious since i've had for over 10 years, but it does have a huge impact on your life.
I do experience the heavyheadedness that you mentioned, but I also have next to no balance, is this your case as well ? I get dizzy spells rarely, or at least severe dizzy spells rarely, I get dizzy spells pretty often, but they feel as if I suddenly sink one foot into the ground, and that's it. The more serious room-spinning episodes don't happen often, maybe once a year, it used to be more often when I was younger.
Naturally, I have anxiety, and doctors assume it's what causes my dizzyness, but I believe it's the other way around, I don't get dizzy spells when i'm having an anxiety attack, or when generally feeling anxious, it happens randomly, and then the anxiety comes in from worry.
I think you might be right about it being a condition that has not been discovered, or that isn't possible to discover yet. It's sort of a depressing idea, but the neurologist that I saw, said he didn't know what caused my dizzyness, but that I should just try my best to live with it :s he supposed that it might be a diminished cerebellum, but my coordination is fine, except for my balance, which is just rotten, and i'm often questioned about being drunk, when in fact, I don't drink at all because it makes my dizzyness worse. He said it might've diminished so gradually that my coordination was able to adapt but my balance wasn't.
There doesn't seem to be any answers