not going to be close to this thread for a short time. if you have a hard time with the mastercleanse, as it can be hard. try to taper off of it into a juice fast for the rest of the time for your first real try. sometimes you really need to be able to gear up for a fast and let your body get used to something like that. check out
http://www.juicefasting.org/ and see what you think.
but keep going on it at least today and see how it feels.
what is your regular diet like?