How can I get healthy sleep patterns?

I am 16 years old. My sleeping pattern has been irregular since I can remember. It's pretty odd, actually. No matter what, I cannot sleep at night. It's literally 5:12 right now. I was inpatient at a health facility twice in 2010 and the second time, I was diagnosed with insomnia and put on sleep medication. But from general knowledge, and my love of researching things of the subject, I conclude that insomnia is a disorder in which it's difficult to sleep at all. For some, they find it hard to fall asleep for about half an hour to an hour. For some, they wake up too early and are not able to fall back asleep. And for others, to just not sleep for a long period times at once (like a day or two). But that doesn't exactly explain what my sleeping pattern is like. I do find it very difficult to sleep, at night. I wake up for school at 5:30 and get home at 4:30. I am usually really exhausted and tired. I will be ready for sleep throughout my day. But when I get home, take my shower (4:45 to 5:15), eat (5:30 to 6:30), and do a few chores (6:40 to 7:30) I will not be tired anymore. I take hot showers, which I know tightens your skin up and relaxes your muscles so that can't wake me up. I drink water normally. I eat healthily. And I am lazy at doing my chores since I'm exhausted. So I'm not doing anything to jitter me up. I will be tired and exhausted the entire day. When I lay down, watch some tv, I know I won't be able to sleep. I even read most of the time, or write. I don't really do anything exciting. And like I said, this has been happening since very early childhood. I'm not hyper at night, just awake. My muscles are still tense from the day and I'll even have a headache sometimes, so why am I so uncontrollably nocturnal?