Why does my Lumia 625 keeps getting switched off if I press the screen a bit?

[Sampat Aditya]

My phone can't handle pressure. If I press it with my thumb, it would get off. Later, when I restart it, a screen showing a question mark over a battery pops up after the Nokia logo. It is only after a variable period of time that I am able to turn it on again. Recently, it has gone off for days. Hapless conditions. Please suggest something.