Sleeping issues

I have trouble falling asleep, and I usually fall asleep around four or five in the morning. I sleep for about three to four hours a day during the week, but on weekends when I don't have anything to do, I can sleep for 16 to 18 hours straight. At night, I'm often plagued by intrusive thoughts about my future and past. I don't enjoy dwelling on these thoughts, as they feel like a waste of time.

I don't know how unhealthy or wrong it is, I'm just stating a fact. I'm supposed to wake up in three hours.