iPhone 4 screen won't work after repair

I had a broken iphone 4 and the screen still worked after I cracked it. one day I spilled a glass of milk on it and I got the milk out because it was cracked. It continued working after that. Now the iphone turns on but the touch does not work. I figured it just needed a new screen so I ordered a screen and try to replace it but with the new screen it did the same thing. Anyone know what my problem is?