First of all what are you expecting in just 5 days? It takes the first 3 just to empty the system out and now your system is just at the begining stages of just adapting and it's around 8 days before your system starts do any cleansing worth mentioning. The scale is no indication of success on any fast and depending on how your system retains fluids your weight can vary quite a bit in just the course of a day. This being a cleanse the system will do what it need to address the most first and many times it won't be weight loss. Ditch the scale and press on!!
You are absolutly correct about gaining weight after fasting. This has little to do with calories but more from the >FACT< that >ALL< forms of fasting will slow the metabolism down and if you go back to your old habits and not exercise to bring the metabolism back up you can gain back more that you lost. The whole weight loss succes when you use fasting is totally predicated on what you do after the fast is over. Without a follow up plan it is a sure fire plan for failure. You system will be operating more efficiently getting more nutrition from less food and then you can continue to loose weigth in a safe a permanent manner.
10 days is the MINIMUM so you can't expect any miracles and certainly much less in 5 days. You are doing your system a world of good and the scale will not tell you real story. Ditch the scale and press on persevere and look forward and plan what you will be doing and eating >after< the fast is over.