Cursor moves in a weird way when playing

[Prof.Mudkip]

Okay so I wanted to play tekkit with some friends but when I try to move my cursor the cursor moves randomly. 

My sensitivity is at 100 i have tried turning it down, reinstalling, and messing in settings. i have heard about disabling something about DPI scaling but I don't know how to do that and some of the help is from about a year ago and i dont know if it still works.