Do you have big boobs? The gravity force of them could be throwing it off, especially if the head above them is dense. JUST KIDDING! I believe that asking God(or the spirits that make up God) before you go to sleep can help relieve your uncertainty and much more. It has for me, in the past.
The pendulum is going everywhere erradically because your mind and thinking is erradic. Instead of using it to find answers or to affect change over circumstance, use it to just open the third eye, that which looks within. To look within you will have to not think and see. You cannot see what is if you want to see what isn't. If you want to see what is, and it is a desert, wanting to see pools of water will not allow you to see what is.
Mine hasn't changed it's movements since I have been using it but I always ask a simple question beforehand to check.
