Question: what episode of one tree hill does haley find out she's pregnant

title: One Tree Hill (season 4)
text: This season focuses on the final half of senior year at Tree Hill High School . Nathan and Haley find out that they are going to have a baby . Lucas starts writing a novel , while also questioning what really happened on the day of the school shooting . Nathan gets involved with some shady characters after he and Haley start having money problems . Peyton finds out she has a brother , but he may not be who he says he is . Brooke becomes friends with Rachel and starts a relationship with newcomer Chase . Dan tries to get close to Karen and help her with Keith 's baby .