There's your problem, suddenly going from 500 calories a day and no carbs, to lots of calories and carbs in one week....that's why your body has retained some water I should think.
Please don't worry I had problems in my first weeks until my body settled into the SW way of eating.
Starting a food diary is an excellent idea, because you can see if and where you have gone wrong, and there are so many of us only too willing to give you advice on you food menu.
So chin up you'll see you will have a loss next week, hugs coming your way, ))))))hugs((((((( X