Sources tell TMZ that Lynne Spears, Kevin Federline and then-manager Larry Rudolph all pressured Britney Spears to check herself in.

Federline threatened to go public by going to court to wrestle custody from her if she didn't go to rehab. Sources say Spears could not withstand the pressure from her mom, Federline and Ruldolph, and checked into Promises last February 20.

After leaving Promises, Britney began getting angry that she was at a rehab facility in the first place. Britney and her assistant, Allie Sims, called Promises multiple times, asking for a copy of the report showing that she tested dirty for drugs and/or alcohol when she checked in.

It took several days to get an answer. Only two reports were sent to Britney's rep, both showing no drug or alcohol use whatsoever. Most shocking, the first reported was dated March 7, 15 days after Britney checked in.