Tiredness / Insomnia

I am 18 and for all my life I have had issues with fatigue and sleep. My parents even paid for various tests to be ran on me when I was just a baby but the doctors found nothing wrong with me. Fall asleep has always been difficult for me. It doesn't matter whether I'm wound up before bed or am dog tired after days of 4 hours of sleep if that. However, even when I do manage to get it, I never feel rested. I still feel tired and fatigued and I'm fed up with it. It continues to affect my performance and how I live my life. I just want to feel awake and aware but I can't. I'm not sure if it's necessarily insomnia problem because even when I do manage rest, I don't feel it, but I do know that it is something. Also, I have no idea if this is relevant or not, my guess is that it isn't but just in case, I occasionally get dizzy spells where the whole room spins and for no reason. There are very rare and infrequent, like twice a year, but they happen for no reason. I could be laying down and suddenly the room starts spinning. If anyone could give some advice or thought I would surely appreciate it.