You will not find any difinitive answer as to X is the amount everybody should drink, because it varies with size, activity, etc, and frankly different experts vary with their opinions, as in any field. You can find any 1 research article to support any one side. It would take much longer than the time you spent to fully research that answer. Since I do not sit in front of a computer all day, I cannot direct you to a specific article, but I have read them and it is common medical practice. Also, the fact you are dizzy every time you stand up-*IS* an indication you may have volume depletion, and could be verified by taking postural vitals. Stress doesn't help, but honestly, if you are having that kind of symptom, it might be a hint you are not getting enough water, no matter what is recommended.