To much of drifting...!

Hello Gentlemen,I recently did a reinstall FS9 , but one thing which has come to my notice is that my joystick seems to have become very sensitive , which it was not before and also i have kept the sensitivities same as before , however iam not sure about the 'Null Zone'..Also , when even iam not holding it the aircraft seems to move left or right....God knows why.....And whenever i hold the stick also it wavers a lot and its getting difficult to fly the aircraft and landings are always going bad..!!Can anyone tell me why this is happening..Thanks for any help!RgdsAtamvir