Go see a good doctor that will be thorough in checking all other probably causes of fatigue. You should probably end up seeing a few specialists as well. The

Go see a good doctor that will be thorough in checking all other probably causes of fatigue. You should probably end up seeing a few specialists as well. The major symptom of CFS is post-exertional malaise, meaning you feel worse after sufficient exertion. While you wait through what may be many months of medical testing before everything is ruled out, you might try an experiment. Exercise usually helps depression, but usually worsens CFS. Try a bit of gentle exercise, and work your way up gradually over time until you can sustain some intensity. If that improves your fatigue, that's good news, it could be depression, and keep up the exercise. If you feel worse, more depressed, confused, fatigued, with trouble concentrating, that could be post-exertional malaise. Try taking it extremely easy for a few months (maybe many months). Don't do anything that feels like you're pushing yourself. If you start to feel better, if your fatigue and mood start to lift, and you are able to concentrate better, then it could be CFS, and keep up the gentle pacing. Also, if your fatigue came on after a relatively severe viral infection, that would point to CFS as well.