I Am Wondering What Could Be Causing My Dizziness. For

I am wondering what could be causing my dizziness. For almost a year now I've been experiencing dizziness that feels like I am walking on a boat, sort of imbalanced. I also feel tingly at times like one feels when they've had too much caffeine, though I'm been caffeine free for a while now. Sometimes it seems as if I have a very high pitched ringing in my ears, though I can't be sure if that's true or my imagination. The dizziness/imbalance comes and goes. I've not experienced any in the past three days, but prior to that I had been feeling dizzy most of the day for four days straight. I call it dizzy, but it's more just imbalanced and my head feels foggy. I've had an MRI which came back normal. My blood work has all been normal. My ENT had my hearing checked last October which was also normal. The ENT and also a vestibular rehabilitation specialist checked to see if had BPPV vertigo by maneuvering my head and body, but that too was normal. (I did have one episode of vertigo in July of 2015 that lasted for about 30 seconds when I turned over in bed one morning.) About ten years ago I had a case of erythema nodosum. My current doctor is going to refer me to a neurologist, but I'm thinking it might be something simpler, like maybe an issue with my amalgam tooth fillings. Can you offer any advice?