My Macbook Won't start

My macbook had a few problems, it was slowing down a bit when running firefox, and it woul sometimes need a key-mash and patience for it to restart after I closed the lid.

But yesterday, it wouldn't restart at all after I closed the lid. The apple light at the back came on, and the screen got a bit brighter, but there was no picture, I left it open all night for the battery to run down. When I came down the next morning, I plugged it in, and turned it on by holding the on key, and it still wouldn't start. I can turn it on and off by holding the on button for 5 sec, but no other way, but the only way I can tell it's on and off is by the screen becoming slightly brighter (but no picture at all), and the apple light at the back turning on. Other than that, the caps lock key light worked last night, but not any more, does anyone have any idea how to fix this?

I have steps 4 and 5 from this list, but it doesn't change anything http://www.macworld.co.uk/how-to/mac/steps-take-when-your-mac-wont-start-3423817 /