Why is Joe Hurt?

In chapter one we see Joe mournign the death of his father, and experiencing wierd flashbacks. In Chapter 3, Joe realizes that the doctors have cut his arm off. What hurts Joe the most is that he does not have arms, legs, a mouth, nose, eyes, and that he can't be dead. At this moment, I think that Joe should have been more worried about his arm, but no, he was more worried about the ring his girlfriend Kareen gave him is on the hand that was just cut off. It is at this time that Joe experiences another flashback, where Kareen's father Mike, orders them to spend the last night together in her room. I think that the memories serve as an escape from his pain. Many more memories like this occur in Book I, and it becomes difficult for him to comprehned what is reality, and what is a dream, as we saw in the instance of the rat chewing on him. What hurts Joe is the fact that he is literally treated like a science experiment, and that he sometimes just wants to die.