Does dowsing with a crystal pendulum work?

i have done it for months using an amethyst on a silver chain and i have worked out yes and no ways and i have tried to confuse it just to make sure the answer was right. anyway...for the past few months its been true now its starting to lie to me. am i doing it wrong? im confused. clockwise is yes anti clockwise is no. its usually correct but now its confusing me and when an answer was yes before now its no when it should be yes. what do i do with it? i feel to snap it in half im so angry.