The Britney BACK IN REHAB...3rd time in 2 weeks

Faced with the very real threat of losing custody of her sons, the Britney caved in to pressure from Kevin Federline and checked back in to rehab on Thursday morning, she was driven to Promises by her mother.

As a result of Britney's decision to get the help she desperately needs but is reluctant to receive, Kevin has agreed to cancel today's previously scheduled emergency custody court hearing.

If Britney leaves rehab before getting full treatment, which is expected to last a minimum of 30 days, Kevin will immediately go to court seeking orders allowing him unquestioned full custody of the children.

A crazed Spears arrived at Federline's house last night but he wouldn't let her in.

Both children have been staying with Kevin since last week.

stay tuned...