Nick Gordon says Bobbi Kristina Brown’s drug use ‘got really bad’ after Whitney Houston died

Nick Gordon, who was Bobbi Kristina Brown's boyfriend at the time of her death, has returned to "Dr. Phil" for the first time since he dissolved into hysterics on the show in March 2015 and subsequently went into rehab — and his demeanor is very different. He's also spilling a few secrets about his girlfriend's drug use.

"Rehab was something I needed, and I'm thankful that I got that opportunity," he calmly told Phil McGraw, who'd arranged his guest's treatment last year after their sit-down turned into a train wreck.

Gordon, who was taken in by Whitney Houston when he was 12 and raised as a kind of brother to "Krissi" before she and he became romantically involved, admitted that he'd been using alcohol and Xanax when his sit-down with McGraw -- see a bit of it, below -- spun out of control.

"I was drinking so much at the time because I could not deal with what was happening to Krissi. It mentally broke me. That's the lowest point in my life, right there," Gordon said in one of several clips that tease to a two-part interview set to air Thursday and Friday.

The interview addresses what happened leading up to when he found Krissi unresponsive and face down in their bathtub, and McGraw also poses the direct question, "Did you murder Bobbi Kristina Brown?"

After using drugs "socially" ("smoking a little at parties") before her mother's death, his girlfriend had developed a problem with drugs, he said. Photos of Bobbi Kristina using a bong and snorting cocaine surfaced a few years ago online. Gordon told McGraw that he had smoked drugs with her. Houston and Bobby Brown, Krissi's father, both struggled with substance abuse.

"It got really bad after Nip had passed away," Gordon said, referring to Houston by her family nickname. "It's unfortunate, but at the time that's kind of the only way we knew how to deal with what had happened."

Bobbi Kristina Brown died on July 26, 2015, in hospice care nearly seven months after she was found unresponsive. She was 22.

No criminal charges have been filed against Gordon, but he does face a civil suit filed in July by a court-appointed conservator that initially alleged that he abused his girlfriend, took $11,000 from her and maneuvered himself into a position to control her and the substantial estate she inherited after her mother died.

In August, after Bobbi Kristina died, the $10-million claim was amended to include an allegation of wrongful death, accusing Gordon of injecting his girlfriend with a "toxic cocktail rendering her unconscious" and placing her in the bathtub.

In March, Bobbi Kristina's autopsy report was unsealed. Her underlying cause of death was given as "the immersion associated with drug intoxication."

"Death was clearly not due to natural causes," the report said, "but the medical examiner has not been able to determine whether death was due to intentional or accidental causes, and has therefore classified the manner of death as Undetermined."

After the autopsy report, attorneys Joe Habachy and Jose Baez issued a statement criticizing the district attorney's office in Fulton County, Ga., for helping "feed the slanderous media frenzy regarding Nick Gordon" and his possible role in her death by "failing to acknowledge that there is simply no evidence of any wrongdoing."

"Frankly," the lawyers' statement said in March, "the right thing for the District Attorney's office to do right now is to tell the public the truth ... that this was an accident ... or even a suicide, but not a murder. And the right thing for everyone to do is let Nick live his life now and let Bobbi Kristina rest in peace."

A representative for the district attorney's office did not immediately respond Wednesday to a request for a status update regarding the investigation into Bobbi Kristina Brown's death.

Follow Christie D'Zurilla on Twitter @theCDZ. Follow the Ministry of Gossip @LATcelebs.