How do I get my Mac Book Pro to

I purchased my Mac Book Pro just over 3 years ago and it has never had any problems at all before. I came to turn it on as usual, but when I pressed the power button nothing happened on screen. I thought maybe the battery had run low for some reason/ I'd left it on by accident, so thinking nothing of it I just plugged it in and left it to charge for 3 hours or so whilst I was out. Pressed on button again and again nothing. Thought maybe my battery pack wasn't functioning but then noticed that the tiny white light at the front showing, but not pulsing as it would normally?! No apple light at the back or lights behind the keys. Slight fan noise if you hold it close to your ear, but nothing louder than usual when at standby, ie. no loading/whurring noise audible. Force shutdown by holding on the power button and then holding to switch on to try to reboot it, but this has the same effect, have tried using the shift button (as in the support section) on start up but again nothing at all on screen. I have all my original apple CDs, but unfortunately my Apple Cover has now run out and not all my work is backed up so I would like to avoid wiping the files if possible. If anyone has had a similar problem and knows how to fix it please can you guide me? I am not very good with computers so apologies in advance, Thank-you 🙂