I'm doing the optifast diet and i'm in week 2. everything is great except constant diarrhea. i've also been taking benefiber once a day. advice?

Wt loss is water wt: That is not sustainable weight loss and it can mess up your electrolytes and cause you serious harm! That is like wringing out a water soaked towel and saying "See how much lighter it is!" As soon as you start eating normally again the water will return as will your frustration and anger with your latest fad diet. As has been said in another context "There is no Royal road to geometry."