Britney Spears' Marriage to Sam Asghari in 'Deep Trouble'

Britney Spears' marriage to Sam Asghari is on the rocks ... this according to multiple sources in the know.

TMZ has prepared a documentary that will air tonight, which explores Britney's life post-conservatorship. We're told Britney has gotten physical with Sam and screaming matches have been frequent. We're also told things have gotten so volatile security has had to step in.

Our sources say Sam doesn't stay at their home much anymore and it's especially alarming because of how she has come to rely on him.

"TMZ Investigates: Britney Spears: The Price of Freedom" airs tonight, Monday, at 9 PM ET on FOX.