Don't be surprised about BMs. Your bowels will be full of it and it's all down to whether or not peristalsis is still functioning whether you have them or not.
Ditching the carbonated water would be a good idea and just go for the purest natural water you can get. That carbonation is just an irritant that you don't need to fight with.
I've even heard of weight gain during a fast which can only happen if you're retaining water. Temporary slow downs shouldn't be a problem but it should be taken in context with other symptoms.