I've been feeling minor lightheadedness and back pain for around 30 hours. i've had full meals and plenty of rest. any probable causes?

Many reasons: Lightheadedness after standing up can be due to orthostatic hypotension if your resting BP is too low or you're dehydrated. It can also occur due to bradycardia, or slowing of the heart rate (HR). You could also have some vasovagal component. See your primary care physician immediately for guidance. http://www.webmd.com/a-to-z-guides/hypotension-orthostatic