Britney Spears has been in rehab for two weeks, but doctors are still concerned about her condition. "They're in shock at what bad shape she's in," says an insider.

Another source tells Us Weekly that since Spears checked in to Promises Residential Treatment Center in Malibu, California, on February 21 (for the second time), the 25-year-old pop star "has been getting in tons of trouble."

The singer has been reprimanded for making cellphone calls, has left the facility to shop, and now she wants to leave rehab for good.

"She's convinced she's suffering from postpartum depression and does not think she has an alcohol or drug problem," the source says. "She's angry at her family and her manager for pressuring her to enter the program. She feels she was ambushed."

However, according to reformed wild child Courtney Love, whether or not Britney gets better is entirely up to Britney: "You don't stop until you want to stop," Love tells Us. "You can't make someone stop."

(Spears' rep had no comment.)