My iphone screen is lots of different colors when i turn it on

For a while now my iphone has been flcikering and jumping about, i didnt think much of it but when i did i turned my phone off to try and see if it would make it any better but when i tried turning it on again the screen was just loads of colours( sometimes white, black, and other colours) any suggestions as to what has happened and what i can do to fix it?