Is it only triggered by light changes? Interesting. That makes me think it is related to cranial nerves or a sympathetic nervous system response. It's not a blood sugar thing right? Is it when you turn your head to the side (as in ear to shoulder) or look up at the sky? There are these little crystals in the trochlea that can become dislodged and an EENT doc can painlessly roll them back into place. That disorder is called Benign PPV. But dizziness is nothing to take lightly. I recommend getting a work up. Let us know how it goes.
Hello~I hope you are feeling better, but if not, I suggest seeing a chiropractor, you could have some misplaced vertebrae in your neck, and if this is the case, you will certainly have the dizziness you have described.
He/she will take some x-rays, study them and then discuss the findings, after a few treatments, you should start to feel a lot better and be dizzy free.
Is it more in the morning or when you stand up?