Everybody's body is different. I'm currently on day 8 of the Classic Reboot. I used to eat really well, then things changed and I was taking in a lot of sodium so I KNOW I had some water weight to shed. Personally, I dropped 3 pounds in the first couple of days, but I'm not so naive to think it was actually pounds being shed. Don't be discouraged by the scale, and put it away if it's not helping you along.
Some thoughts though- make sure you drinking enough water. It drives me crazy to because I end up peeing every 15-30 minutes, but it's so important.
Make sure you drinking enough juice. It's still calories, and if your body doesn't think it's getting enough energy to get through the day, you won't see any weight loss because it's holding on to the few calories you're giving it.
And lastly, day three was rough for me too even with being able to eat meals at that point! It's rough for everyone, from the sounds of it! But take it easy and make sure your juices are mostly vegetables with some fruit (80/20 veggies/fruit). It'll help keep your sugar levels more moderate without spikes after a juice and then a massive crash later on.