Hey Sabrie,
Under this device's battery (right on the floor of battery's bay along with the SIM card's slot) is a screw that comes originally covered with a little blue round paper sticker on the head. This screw which holds up the track-pad's mechanism tend to loosen during the device's day to day usage. Removing the blue round paper sticker and fastening this one screw is all it normally takes to get your phone's track-pad back to functioning as it should be.
Source: http://mobilephoneissues.blogspot.com/2013/12/sluggish-or-unresponsive-blackberry.html
