Have you considered whether or not you might SAD - Seasonal Affective Disorder. That's very common in northern climates due to the inability get outside often enough. We used to live in Iowa and I had that -- winter time was disasterous for me.
Beyond that -- have you been tested for thyroid antibodies? It's possible to have an autoimmune disease, that won't show up with just the standard thyroid tests of TSH, Free T4 and Free T3, but could still cause symptoms.
Please also see if they have tested vit D and B12 levels. I understand both of these could also be a possible contributor to your symptoms, if they are low.
Please post your TSH, FT4, FT3 levels. The standard for 'normal' has changed, and many labs are still using the old system.
:) Tamra