Blood tests next week... AGAIN

So friday I had to do some blood tests because I've been beconing lightheaded when I stand after sitting or lying down, even for a short period of time. So it was decided I had orthostatic hypotension, which is common in the elderly population. So she reccommended more sakt and calcium intake, and had blood tests ran to make sure my thyroid and whatnot was ok. So they called today and my thyroid is normal, but there was some results that they were slightly concerned about so they wanted to run tests again. The problems was with my kidneys. I had kidney issues as a kid and had to see a urologist a lot as a kid, and it was horrible. But I've been feeling worse, light headed, and sick, and really tired, even if my day just consisted of sitting and watching tv or reading. Walking up the stairs is like a marathon lately. And I don't know why. And it scares me a little... I hope the results I get from next weeks blood test just show it's slight dehydration so all I need to do is drink water, but really I've been drinking water and tea like a horse.... I'm worried there's something wrong with me... I don't need another stress with school starting tuesday... I have 14 credit hours, and I can NOT miss any school just because I'm feeling a little woozy.