Constant crashes and graphical issues after updating to Yosemite

This problem started gradually. First a game I tried to launch crashed. Then I was unable to open any applications at all. I restarted the computer after having to force quit out of everything. The user sign in screen would let me type in my password and then I would get a white screen. I restarted twice more before being able to log in. Then the graphics problems started. No online videos would play. I tried opening a different game to see what would happen. That froze and made me have to restart again. The first time I got a grey striped screen. Then when I was able to log back in I got an error saying something like "a graphics problem has been detected."

I have tried.

1. Restarting
2. Hardware diagnostic test
3. PRAM reset
4. SMC reset
5. A second user account (logs on but I haven't been able to test it by loading a game or graphics intensive program + it's not a real fix)

Still running into the same problems if I do much more that web browsing.