apple ipod 4

my ipod isnt working, the appes crashes, or it kisks me out, and now some of the screen is working. Ex. only half the screen is touchable. i tried to go back home and the little square is there but i cant move it let alone click it. i dont know what to do i tried to turn it off but even when i do turn it on its starts doing the same thing. i cant even type. i tried typing in the letter "E" but it wont let me, and i cant press send. What do i do? do i need a new one? in other words my screen isn't working...