I have done a 80 day water fast before I know what you are going through. Here are a couple tips when you stand up do it slowly and stand their while the dizzy spell fades. Try to learn to enjoy the feeling. It should start to fade away tomarrow which is day ten. Day ten is when you body kicks into full ketosis mode. Your ketone level and growth hormone should be evening out any day now.

"After thr third day of a fast, the body begins to make ketone bodies in the liver (Enter Ketosis). In the absence of food (Energy,) Ketone bodies are produced by the body as an alternate energy source. Normally, ketone levels in the blood are less then 0.2mm. After several days of fasting they approach 3.0mm, and steasily rise thereafter. Importantly, never eat, even an extremely little amount of food during a fast. This will quickly shift the body out of ketosis, back to its normal metabolism of glucose (food), decreasing ketone bodies, decreasing growth hormone and increasing hunger."

"(feeling light headed, at times, is not uncommon). During day 5-10, energy levels very noticeably improve after day 10, with sharply elevated levels of both growth hormone, and ketone bodies, energy levels are tremendous,as is mental clarity."