Am I nocturnal or an insomniac? Is there a difference?

Sounds to me like you have got your circadian rhythm all out of whack. Simply put, if you sleep during the day then your body is not going to need to rest at night. You would have to stay up all day to be able to sleep at night. Also, you sound like a true night-owl. I, myself am the same way. I prefer to live at nightime also, but a functioning adult in the real world must get up and go early morning hours. That's why I'm studying to be a Polysomnographic Technician. Work night shift and sleep during the day just like I want and nobody will call me lazy. Hope this helps!