I've been struggling with this for a long time. I can sleep 6, 7, even 8 or more hours, and still feel tired and drained in the morning. If I try and sleep too long (more than 7 hours), I feel hung over as well as tired, and develop a headache. I don't wake up in the night, don't snore, don't dream, and have only mild insomnia falling asleep at night. My last doctor prescribed zolpidem (ambien), which didn't help at all, and may have only made it worse.