My laptop Lenovo U430 won't turn on after putting it to sleep mode?

This has happened before. I put it into sleep mode, come back later and then the power button has stopped blinking like how it's supposed to when its on sleep mode. When i press any key or press the power button nothing happens as if the laptop is dead. When i plug in the charger the light saying its charging still comes on. This is the second to time it has happened. The first time i just waited a few hours and came back and pressed the power button and it turned on. This time i've waited two days and it still doesn't power on as if its dead. Any help?