Game shutdown repeatedly.

Today morning, I start playing minecraft, when i load my world and hulting around my house, suddenly my game crashed. I thought that was just a force closed, and then i reopen my game and again when i move to my left of my house it happend again, my game closed. Afterthis I make a check, I reopen my game and move towards right side of my househouse, my game runs but there is some lag. Afterthat i moved to left of my house and my game closed again. And one more thing is when my game close suddenly it is not saving my last movements  .