Why do i get really lightheaded when i get up first thing in the morning? my vision goes dark and i hear ringing, sometimes i fall back down but i'm fine for the rest of the day?

After lying in bed all night if you rise to a standing position too quickly, your cardiovascular system sometimes does not compensate quickly enough and you become dizzy, your blood pressure drops somewhat and you can experience the other symptoms you mentioned. If you will sit on the side of the bed for a short time before standing it can prevent this from happening.