Brittany Cartwright started secretly hooking up with Jax Taylor’s pal Julian Sensley shortly after separation

Brittany Cartwright started secretly hooking up with one of her estranged husband Jax Taylor’s pals shortly after their separation, Page Six can exclusively reveal.

We can confirm that, after the “Valley” stars announced their split in February, Cartwright began a “casual” physical relationship with basketball player-turned-actor Julian Sensley, who used to work the door at “Vanderpump Rules”-affiliated bar TomTom.

We’re told Cartwright, 35, and Sensley, 42, only ever hung out privately and that their romance is now over.

An insider tells us that Sensley and his now-fiancée — who share a young child — had been “off and on” and were “going through a rough time” when he and Cartwright were intimate.

Brittany Cartwright started secretly hooking up with one of her estranged husband Jax Taylor’s pals shortly after their separation. brittany/Instagram Page Six can confirm that, after the “Valley” stars announced their split in February, Cartwright began a “casual” physical relationship with basketball player-turned-actor Julian Sensley. NBAE via Getty Images

Sensley, who was once rumored to be linked to “Vanderpump Rules” star Lala Kent, is also the dad of an older child.

When Taylor found out about his estranged wife’s fling with Sensley, we’re told he “went berserk” and had a “psychotic breakdown,” which contributed to his desire to seek mental health treatment.

The “Vanderpump Rules” alum seemingly alluded to the tryst in June in a since-deleted X post that read, “you may want to ask brittany who she’s been sleeping with for the past 4 months….”

The drama will play out on Season 2 of “The Valley,” we’re told.

We’re told Cartwright and Sensley — who got engaged to his long-term girlfriend last month — only ever hung out privately and that their romance is now over. An insider tells us that Sensley and his now-fiancée had been “off and on” and were “going through a rough time” at that time. Twitter/SensleyJulian

Reps for Cartwright, Sensley, Taylor and Bravo did not immediately respond to Page Six’s requests for comment.

Taylor spent the majority of August at an inpatient mental health facility, explaining to fans beforehand that he wanted to work on his “serious anger issues” and “get better” for his and Cartwright’s 3-year-old son, Cruz.

Upon returning home from the treatment center — where he was diagnosed with bipolar disorder and post-traumatic stress disorder, and learned he’s a narcissist — Taylor was handed divorce papers.

When Taylor found out about his estranged wife’s fling with Sensley, we’re told he “went berserk” and had a “psychotic breakdown,” which contributed to his desire to seek mental health treatment. / SplashNews.com The “Vanderpump Rules” alum seemingly alluded to the tryst in June in a since-deleted X post that read, “you may want to ask brittany who she’s been sleeping with for the past 4 months….” NBCU Photo Bank via Getty Images

A few days later, Cartwright addressed the divorce on her and Taylor’s joint podcast, telling their listeners, “It’s taken me many, many years to get to this point where I gained enough courage and strength to do what’s best for me, get myself out of a toxic relationship and ultimately see my worth.”

Though the Kentucky native was the one who first filed to end the duo’s five-year marriage, a source previously told Page Six that Taylor was “100 percent on board” with the decision.

Cartwright told her co-stars on the Season 1 finale of “The Valley,” which aired in June, that the former model — who admittedly cheated on her when they were dating — would become “mean as a f–king snake” while fighting off frequent hangovers.