Sources with direct knowledge tell TMZ ... about a week ago, Sam confronted Britney over rumors she stepped out on him. We do not know if the rumor has any basis in fact, but we're told Sam believed it and the 2 had a huge fight.

Our sources say Sam has moved out of their house and is now living in a place of his own. As one source put it, "It's only a matter of time before Sam files for divorce."

TMZ broke the story, there's been "deep trouble" with the couple's union for months ... Sam wasn't sleeping at the house much, and we're told Britney has gotten physical with him in blowout fights that include frequent screaming matches.

As we reported, Britney has a prenup which protects her assets, but one insider tells TMZ, the likely end to the marriage will be a check from Britney to Sam that will settle things, at least financially.

If you've been following Britney's journey post-conservatorship, the writing's been on the wall. At times, Britney's behavior has been erratic, and we're told Sam was over it.

Sam has publicly defended Britney from critics, but privately we're told he was frustrated ... at wits' end.

Sam and Britney started dating back in 2016, when he got a gig in one of her music videos. Since then, they've been practically inseparable.

Amid the #FreeBritney movement, Sam often expressed support for Brit's fans ... she shared plans of marrying him and starting a family. He even posed in a Free Britney t-shirt, which he posted to his Instagram.

Britney was ecstatic when Sam popped the question in September 2021 ... sharing pics and video of her ring and happiness with her fans on social media.

Eventually, Sam and Britney said their "I Dos" and tied the knot in a small private ceremony at their Thousand Oaks home -- not without drama, courtesy of one of her exes. Still, the ceremony itself seemed to go off without a hitch ... and they appeared happy.

While divorce docs haven't been filed yet, we're told that should happen sooner rather than later.