A 28-year-old female presents to a psychiatric clinic 5 weeks postpartum. She reports persistent depressed mood, severe insomnia even when the baby is sleeping, inability to eat, intense guilt about being a "bad mother," difficulty bonding with her infant, and frequent crying episodes. She also reports intrusive thoughts about accidentally harming her baby, such as dropping him while walking down stairs, which cause her severe distress. She states she has never wanted to hurt her baby and these thoughts frighten her. She has been checking on the baby excessively and has asked her mother to hold the baby because she fears something will happen. Her EPDS score is 21. She has no prior psychiatric history and no psychotic symptoms. Her pregnancy was planned and desired. She reports that her symptoms began approximately 2 weeks postpartum and have progressively worsened. What is the MOST likely diagnosis?