Usually days 2-4 and day 7 are the worse for some people. Of course it varies depending on the person. My first fast I was feeling horrible for five days in a row. And on my current fast I am only having minor symtoms. Of course I'm only on day 2 so we'll see. Heh.
On the comment about doing a bowel cleansing, Different people say different things. Some people think you should do "cleansing" everyday why others feel you should do it when you feel the need to do one. I am in the latter. I don't do enemas or laxatives <---(have horrible reactions to them), but I plan on doing a salt water flush every once in awhile when needed.
I'm not much of an expert on enemas, but I've heard some people say they take them almost everyday during a fast. Where to buy them? I have no idea. lol. You may want to try: http://freedom-you.com/BB/ for enema support. Alot of people there use them. Hope that helps. =)