Minecraft graphics will not work.

Minecraft has always worked good on my computer, not many problems, but since minecraft 1.8.1 my graphics will not work, it glitches out, flashes, you can see through the ground, stuff appears then disappears. Random colors, even the images for the acheivements will not work, everything just looks like a huge mess. I find it very weird because i never ever had this problem before and ive been playing for years on the same computer.