how can i fix the touch screen on my sony ericsson p910i?

When I try to activate an icon on my touch screen it activates a different icon higher up on the screen. i.e in order for me to activate the contacts icon i have to touch and activate a icon two places below the contacts icon in order for it to be activated. This also means that i cant activate the icons at the very bottom of the screen as it avcivates the ones above. in other words the touch screen has configered itself higher than the icon which have stayed in the same place. please help if you can, thanks