So my macbook pro was working perfectly fine half an hour ago... I shut it down and it wont turn back on. If i hold the power button in it turns on (like I can hear it) and immediately shuts off...The screen stays black. I tried taking out the battery and power cord and holding the power button for 30 seconds. I also tried starting it with just the power cord and no battery in, and the other way around too and it still just turns on for 2 seconds and immediately shuts off....what is wrong? what should i do?