Vitamin D (d3) levels should be evaluated. Vitamin D levels are going to decrease during witner months. Vitamin D (low) is associated with immune, neurological and many more problems. There is a .org site devoted to vitamind d issues.
Tests that will help:
1. Heavy metal challenge test from Doctor's Data
2. Hair analysis from Trace Elements Inc.
3. Amino acid profile (serum preferred) by Metametrix
4. If you have GI problems and that is where some of the problems started do the GI Effects Test from Metametrix.
5. Dr. Patricia Kane offers a fatty acid profile which could be beneficial and Metametrix offers an organic acids test which can pinpoint some problems.