I felt like that for the first 2 days. I drink more water and add a laxative tea like Senna in the morning and the evening. The veil does lift. I usually get a nice headache the first or second night, but after the third I'm home free. I attribute it to a lower calorie intake, and also I think the organs in the body are so used to our "regular" diets, that when you put them through a change, it takes them a while to adjust.
Use your best judgement. If the water and the tea doesn't help, 3 days of a fast is nothing to sneeze at. Maybe next time you could do five.