Hello~From the description of your symptoms, I would highly recommend seeing a chiropractor; your neck and upper back could have misplaced vertebrae, this in turn will certainly cause the dizzy/lightheaded feeling you are having.
You mentioned that you had blood tests done, including one for diabetes, did they draw one for an A1c? this will show what your sugar levels have been doing for the last three months. I say this because some of your symptoms do sound blood-sugar related.
Also, how about food allergies, they, too, can cause these symptoms.
I would ask for a food allergy panel, a chemical allergy panel, and A1C, and then also see a chiropractor. If you can not get a doctor to do the tests, then seeing a Naturopath would be a very wise decision as your next course of action.
I have hypothyroidism myself (Hashimoto's thyroiditis) and my symptoms always rule over a lab test. Something I know very well from experience! There are many many comments online of hypothyroid symptoms with "normal" lab ranges. As a general guide however, the Free T3 and Free T4 should be above the median (middle) but below the upper end of the laboratory normal reference range.
Excerpt from Nature Endocrine Solution article - "Is There A Connection Between Hypoglycemia and Thyroid Conditions?"...
"Another potential reason why hypoglycemia is more common in people with hypothyroidism and Hashimoto’s Thyroiditis is because thyroid hormone impacts the liver, and a compromised liver can lead to the development of hypoglycemia. Excess glucose is stored in the liver, and so if the liver isn’t functioning properly then the storage of glucose might be affected."
It is quite common for thyroid patients to also have low B12 (look for levels below 500) and/or Vit D deficiency, both cause a whole range of symptoms