Pretty much what the title says, my game is running at 2fps and struggles to even load into the main menu but runs fine when I tab out of the game. When I tab back in then the game runs fine at 60fps for maybe 2 seconds before going back to constant 2fps. Zombies runs fine, no trouble whatsoever. I've tried reinstalling the game and removing all my custom textures but other than that I'm not sure what to do.