Mighty.Sun.Tzu
Hello Chris :),
Weakness and light headedness are very common symptoms of fasting and the associated detox and should not in themselves be considered reason to curtail the fast early. If it was me, i would continue dry fasting until the thirst became moderate and persisting or slightly more than moderate and persisting if you are experienced and more familiar with the way your body responds. if heavy and persisting thirst was reached at some point before the 5 days, i would not recommend waiting too long trying to reach 5 full days. i base this advice on personal experience with waiting too long on 2 separate occasions and experiencing some weighty consequences, namely in one instance 16 days of nausea.
Best wishes,
Mighty Sun Tzu