Lumia 920 touch spmetimes stops responding

Guys, am having a problem with my lumia 920 sometimes the touch just stops working. if i remove the battery and put it bag it will start working again. sometimes it will work for just a few seconds after i replace the battery, sometimes it will work for a whole week. what could be the problem and how can i fix it.

my screen has a crack but its been like that for over a year now but the problem just started recently....