What Causes Frequent Episodes Of Fatigue, Sleep Disturbances And Headaches?

Over the past year or so, I have had symptoms like: fatigue, tiredness, sleep disturbances, headaches, sore throat, lack of concentration, weight loss, confusion, fainting and other such symptoms.. I have been to the doctors several time, and have also been admitted into hospital but nothings come of it. I have had blood tests, ECG, EEG, MRI and CT scans in order to find out whats wrong with me but they have all come back clear although I still don't feel right.. can you help?