you need to be tested early in tho morning for TSH, FT3, FT4, T3 Uptake, and TPOAB, TGAB. You may be hashiomoto's.. this is a nasty hypothyroid causing autoimmune issue that can start out as hyper/hypo shifting states and end in complete destruction of your thyroid. dizziness, and such are symptoms of hypo thyroid and there is also the chance that you can test negative for hashi's and still have it.
So get the tests run. Get a copy of your lab results and post them.. then we can tell you if something is up. Other things to look into are you B12, Vit D, and Ferritin levels. Low and subpar levels of these minerals/vitamines can cause some of the dominant thyroid symptoms as well.
If we learn by our mistakes, I am working on one hell of an education.