Pain in joints after breaking the fast

Hi guys,

I'm in the second day of the post fast, after six days of fasting and I also have a hard time - strong pain in the right foot(joints I suppose). I believe it is not a food problem, because I broke the fast with juices and then fruits(tomato, carrot, water melon, strawberries). I took each 2 hours a glass of juice in the morning of the first day and in the afternoon I started eating the fruits.
Actually, the pain in the right foot came during the 3 day of fasting, but it was negligible then, becoming stronger and stronger as I was breaking the fast. Does anyone have any opinion or explanation what's going on with me?
Thanks, Dedov.