Im really worried that there might be something wrong with my head?

I've been having similar symptoms (especially the constant tiredness, the dizziness and the short term memory). It may be a lack of iron, particularly if you're a female. And I find that a lack of sleep does make it a whole lot worse. I'm a teenage student and whenever I have to study late, I find that all those symptoms appear, and worse when it's "that time of the month." One other thing...it is likely a lack of water as well. I have to make myself drink because I normally don't feel like it, but headaches and memory problems are often your brain (and body) crying for water. I hope that helps...but do see another doctor just in case it's something else. :)