Alvita is a good brand...it could be your body is already reacting to the mere notion of fasting and the tea is creating chemical changes which signify to parasites and yeast, that the party is over for a while. parasites seem to activate cravings when the food wagon stops.
You will be fine and glad to have you on board. We are having a summer long Master Cleanse party and as long as you bring along a sense of humor, you are in for a ride of your life, one which will hopefully bring you the changes you hope to see.