iPhone 4 screen randomly presses everywhere?

I recently replaced my flex cable as the button stopped working. I put the phone back together and when i power it up the screen is sort of unresponsive. I'll try to slide the bar but it wont respond. I'll finally get in and it's like some one keeps tapping the screen. It's not in a specific area. It's like someone is tapping it everywhere. I believe its because the screen got dirty and finger prints on the back on the mirror like surface. Would that be the problem? Thank you!