"I think a lot of that is hormonal and I'm not used to being around so many people all in a confined [or] a small space for so long," she said.
"I'm used to going [out] all the time."
The expectant mum says she also struggles without having quality "alone time".
"There is not really anywhere to go besides my car," Perry said.
"So, I go to my car a lot. That is my safe space."
Perry announced her pregnancy with actor fiance Orlando Bloom in early March, and unveiled her bump in a music video.
The on-and-off couple met at the Golden Globe Awards in 2016 and their baby will be the first for Perry.
Bloom is already a father to 9-year-old son Flynn, whom he shares with ex-wife Miranda Kerr.
