I had something like that forever. Chronic fatigue, headaches, foggy memory, muscle pain. It all built up to actual chronic depression. The kicker is that im, as far as tests go, stupid healthy. I even exercise regularly. I've been to doctors on and off but the prescription was all sleep (get plenty), exercise(boxing six times a week), eat better (eat pretty well all things considered) Etc.

Since I kept getting politely told it was in my head I kept up my slow stream of research and personal experimentation.

I finally had a breakthrough earlier this year. I realized that my stomach was misbehaving more and more than it used to. Thought maybe I was lactose intolerant so I Stopped drinking milk. Holy shit did I feel better. Thought for sure that it was milk. Felt bad after having some cookies. Assumed it was the low milk content in them. Cut out anything sweet since most sweet things have milk. Cheated in Italy and had cheese and such. Felt fine. Kept cheating. Got a little worse. Had a bite of gelato. One bite. Instant gastronomical disagreement. Finally made the connection between sugar and my mood. Like any sugar. Even overly refined bread is risky. My favorite drink used to be lattes. Of which the steamed milk is practically pure sugar froth.

Anyway. A very large portion of my symptoms have vanished. I can even go back and relate the mopey parts of my journal to particularly refined dietary swings (like when I'm in a high stress time with lots of prepared food)

As soon as I get real health insurance again I'm gonna persue a dietary based inquiry rather than a mood and psychiatric based one. I imagine I can get even better results.