My iphone 5 screen does not respond to touch at all

I don't know what has happened to my phone. The screen does not allow me to even swipe to unlock it. It has lines all the way up the screen of different colours. There is no cracks in the screen or anything like that and I dont recall dropping the phone. The only buttons that work are the home button and the on/off switch. I have tried to reset it but that doesnt work. Any ideas what could have happened and what I can do?