What two things are difficult for Bruno when he changes into the striped pajamas?

When Bruno changes into the striped pajamas, he struggles with the loss of his identity and the sense of individuality that his previous clothing represented. The pajamas symbolize his forced conformity and the harsh realities of his new life, where he is stripped of his former status as a carefree boy. Additionally, he feels uncomfortable and out of place in the unfamiliar attire, which highlights the stark contrast between his past life and his current situation.