Recently I've gotten used to sleeping in the afternoon. I am not talking about a short 30-minute nap, I am talking about a good 3-hour sleep. I usually wake up around 17:00 and feel sleepy/with a headache (I get headaches when I oversleep) for the rest of the day. If I don't go to sleep, I feel sleepy and without energy. I didn't used to sleep that much. During the night time, I toss and turn a lot in bed, have a lot of nightmares, wake up in the morning feeling not rested and not full of energy. Anyone with similar experience? How do I reset my internal clock and fix my sleeping regime?