Take 500,000 IU of D3…yes, a half million IU…not enough to get you toxic, but enough to get you out of the hole the vast majority are in this time of year. Add some B-vitamins, calcium, lots of magnesium, and vitamin C. Discontinue any alcohol and get out in the sun.
Take 100 IU/lb/day of D3 after that as maintenance and see how you feel. Don't put this off, it works within hours. You can get bottles of 50K each online, but right now, just get your hands whatever you have or go to the store. This is readily fixable.
Orthomolecular biopsychiatry… nobody has a chemical pharmaceutical deficiency…fix the nutrition and health and see how your brain responds.