Pilgrim's Inception

This whole book reminds me of a movie called Inception by Christopher Nolan. The movie is about a corporate spy and thief, Dom Cobb, who extracts essential information from the unconscious mind of people he wishes to harm or threaten while they are asleep. To extract valuable information Cobb uses the strategy of dreams within dreams. Billy, in my opinion, has lost sense of what reality truly is because he travels in time with his memories so often. In the movie, the main character has to carry a totem to be able to distinguish reality from dreams but Billy, in the book, does not carry a totem or anything close to it. This idea may sound absurd to many, but I'm not even aware of what Billy's reality is in the book. He believes that moments don't have a definite time lapse, but could our main character, Billy, actually be stuck in Limbo, a subconscious level in which a person loses his/her grip on reality and is trapped for an indefinite period of time? Which is Billy's reality? Is it the war?