It means that your body is trying to dump the toxins released thru the cleansing...
I was trying to remember what Andreas said once, when I asked him same Q you're posing, but instead I just found this in Andreas' Forum:
"If you have my book The Amazing Liver Cleanse, check out the diagrams for the lymphatic system. The main lymphatic vessels, Cysterna Chyli, in the belly button area absorb many of the toxins generated in the intestinal tract (due to poor digestion). This causes lymph congestion (edema) and subsequent abdominal distention. The Cysterna Chyli try to pass their lymph waste and these toxins into the thoracic duct, leading from the belly area up towards the throat where it turns left into the main vein of heart. When congested, the thoracic duct dumps undetoxified waste and toxins into the heart which increases the size of the left side of the heart. This can cause heart palpitations. By cleaning out the blood vessels (through dietary changes) and improving digestion through liver and intestinal cleanses) the heart begins to revert to its normal size and the heart palpitations disappear again. I suffered from life-threatening arrhythmia and collapse, once every 3-4 weeks, while still a child, but they vanished once I became vegan at age 18 and cleansed my body. Now at age 50, my heart is like that of a healthy 20-year old. You can do the same with yours. Andreas"
So, continue LFs, may wanna do some bowel management, para-cleansing, modify the diet, and just press on, don't be discouraged...