Try resetting your smc (steps 1-5), and/or resetting pram and nvram (6-7)
1) unplug the MacBook Pro
2) take the battery out. (use ifixit guides for your model)
3) Hold the power button down for about 10 seconds
4) put the battery back in
5) Try powering up the computer to see if progress was made
**if not, go to 6**
6) Hold the power button down until you hear the hard drive spin down and the computer is definitely off
7) press power button and immediately Hold down Option, Command, R, and P keys. KEEP them held down and hopefully you will hear the computer chime, KEEP holding the keys down until it has chimed 3 times, then release the keys. Hopefully it will boot at this point.
Try this and if it's still dead, maybe something has come loose on the logic board. Open it up and look for unplugged cables, if you find any, plug them back in completely.
Let us know how it goes.