My macbook pro 2011 has a grey screen on start up.

I was running OSX lion when it went blue and grey. so I restarted it, and there was still a grey screen. Then I shutdown the system and pressed command +r and power to get to osx utilities and repair the disk and erase. after I had erased it, I then Downloaded lion and updated it to OSX Yosemite. The system was working flawlessly in Yosemite, I even restarted it a couple time to make sure. I was done for the day and I put sleep on and then noticed that it had froze. I shut it down then restarted it and now its just a apple logo with a progression bar, after the bar get 1/3 the way through it goes all grey. Cannot enter safe mode or recovery mode like before. I have reset SMC and pram/nvram. still no fix. In verbose mode( command + v), it says a couple of warnings like:

Warning: couldn't block sleep during cache update.

Warning: proceeding w/o DiskArb

GPU hardware vm disabled

Is this a hardware issue or an OS issue?

I don't have a reinstallation disk