I've been getting what I would call "pre-headaches", that feeling of almost-wooziness where you know it could turn into pain. I've learned that's my sign I'm not eating/drinking enough. The first day or two I managed to have 2 protein shakes each day, maybe a glass of Crystal light. DEFINITELY not enough. In the next few days it would be more like 1 shake, 1 yogurt, 1 juice. I'm still struggling really, really hard to get enough nutrients to avoid the "pass out" feeling. Maybe this is happening for you too? Do you think you're getting enough fluids?