Why does my screen keep freezing and suddenly become really sensitive?

I am having a bit of trouble with my Sony Xperia E3 phone. Whenever I turn the screen on and click on an app or something nothing will happen. I have to turn it on and off about five o six times before it will pick my fingers up. Also it has become really sensitive and I don't know how to turn the sensitivity down if this is what the problem is. Are there any suggestions on what I should do?