Connections - Chapter Two: Time Travel?

Billy Pilgrim has become unstuck in time. I cannot fathom what goes on inside Pilgrim's head when he becomes "unstuck in time." His delusions of Tralfamadorians and his traveling through time is mind-boggling; it makes me wonder what happened to this wealthy optometrist during that tragic plane crash. Vonnegut writes in such a way that the reader cannot figure out where Billy Pilgrim really is. He could be fighting in the war or he could be at his house, just remembering the war in a prolonged moment of time travel through his mind. What is going on inside Billy Pilgrim's head?