White Screen on MacBook Pro

I have had moments where my mbp screen would "go black" for about 10 seconds, but they were intermittent, and it always came back up to where I was, with no error messages, etc. I am an old PC user, so I don't ever run more than three heavy duty programs at once. I was watching movies through the computer last night, using a cable to view them on TV, and mirroring the screen. When I went to shut it down, a message came up telling me to shut off my computer by holding down the power button, and then restart it - upon restart, all I get is a white screen. No images, no little circle indicating it's working, just blank white.