MacBook won't turn on but lights up

Hi,
For the past few days my MacBook won't turn on. It was running normally one day and then the screen suddenly went black. I held down the power button to restart but it turned the computer off and ever since will not turn on. Until today when plugged into the charger the charger light would blink green, but now it just stays green as if its fully charged. When I hold down the power button it doesn't start up, no sound or picture on the screen at all, but the white light on the front of the Mac appears. On the bottom of the Mac there are no lights indicating the battery charge. The headphone jack now lights up red. Any ideas what the problem is? I'm going to bring it to Apple this weekend but was wondering if anyone knew what this could be... thank you.