BB :: Bold Touch 9900 Screen Goes Dim

I've had my bb for about 6 months now. A few days ago, i noticed that my screen started flickering whenever i used the trackpad to scroll through icons on the home screen.Later, I realised that it would suddenly go dim, i.e. the screen would still show the icons but so dim that the screen looks completely dark., at random intevals.Whenever I pressed the screen lock button at the top to blank it and then press it again to reactivate it, it would reactivate but again at a very dim setting.