i've been facing the same problem. I think it's screen digitizer has some issues.. I visited a shop in my city for the repair. they said. It's screen is damaged. I need to replace it. And it's cost would be 80$. Including repair charges. I came back to home, found some screens on some online stores.. Ordered one form Aliexpress.com in 45$. I have already studied the way how to replace screen in this ifixit.
I have received one lcd screen a few days back. I replaced my self.. And its great.. ALHAMDULILAH... Ifixit :-) its working great.
I am from Lahore, Pakistan.