switching back to home screen

That means that the app you are using has crashed. As a first step shut down your phone, wait about a minute, and restart it. If it continues try reinstalling the app that you are using.

When you are reading what? Can you describe exactly what you are doing when this happens. The only time you should go back to the home screen is when you swipe upwards from the bottom of the phone screen. What app are you reading in?