Laptop screen freeze

I have a DEll Inspiron 630m. My screen has been going a bit wierd of late, every now and then it used to go all pixellated and i would have to reset. Then i realised that if i put my thumb in the corner of the screen it would go back to normal. In the past few days it has done it almost non stop and each time i pressed on the screen or sides of the screen it would go normal. At present i have 2 clothes pegs on the side panels of the screen and everything is fine. Does anyone have a clue as to what is happening and how much or how hard is a fix?