I'm sorry you're not feeling well. :-( Fever is a sign of illness/infection. You may have caught a bug while on this fast, but just in case it's not a bug...
How are you fasting? Are you eliminating and how? Syrup is NOT o.k. while fasting. I know some people here believe it's o.k. to mix Master Cleanse with juice fasting, but I have never read anywhere that this is o.k. Choose one or the other. It looks like you're doing lots of citrus. Sometimes citrus can upset the stomach. I'll post more when I hear from you regarding elimination.