Did you ever hurt that hip joint or something to that region? Everytime I do longer fasts some of my past injuries flare up a bit. Ones that otherwise have been fine for a long time. There isn’t a lot to go on in your post but this is something I notice personally.
I’ve absolutely had that feeling so I know exactly what you’re talking about. Unfortunately I don’t know what caused it or even what made it go away, but try playing around with your salt, potassium, and magnesium levels.
Jesus, please people.. when water fasting you NEED to put 1 teaspoon of Potassium chloride (No salt - salt substitute available at all grocery stores) per liter of water or you will get headaches and risk potassium depletion which could have adverse health risks. Magnesium is good to supplement too but potassium is the most important.