Nope, never had a problem with headaches dizziness or low blood sugar. I am hungry and weak sometimes, but not to the extent you describe. MH posted something just a few days ago about building up the alkaline minerals in your pancreas to avoid sugar problems. If you can't find his post maybe you can ask him. He had some herbs he recommended for that purpose. I do like taking herbs while I'm fasting. There might be some herb teas that would help. He also makes a formula called "concentrated minerals" that might be good to take during the fast.
Giving your stomach a break does great things for your body.