CHAZ BONO’s weight has ballooned to a deadly 345 pounds as he faces a terrifying relapse into a nightmare world of drug-and-alcohol abuse that could cost him his life.

The 43-year-old gay rights activist is planning to complete his trans­gender surgery, but fears the powerful painkillers required could plunge him back into his old life-threatening addictions.

His distraught mom Cher is begging her 5-foot-5 son to avoid the penile construction sur­gery and assured him: “You’re great the way you are – you’re already a man,” disclosed an in­sider.

The “Dancing with the Stars” standout had a scary relapse once before and has admitted: “I’m al­ways afraid when I know I have to take painkillers because that’s my drug of choice and there’s always a risk of relapse.”

The crusader for transgender acceptance was plagued by horrendous addictions for 10 years – suffering blackouts, bouts of vomiting and bizarre hallucinations. But he’s afraid if he follows his mother’s advice and scraps the “bottom surgery,” he’ll never feel like a real man and will have to en­dure a hellish identity crisis, say sources.

The torment is tearing him apart – and his 66-year-old superstar mom is desperately trying to steer him through the crisis.

The singer rescued a depressed and drug-addict­ed Chaz from suicide in 2002, and two years later, she placed him in rehab after he hit rock bottom with his drinking and drug problem.

“She dreads going through that ordeal again if Chaz relapses after the risky surgery,” said the in­sider. “And with his ballooning weight, Cher’s pet­rified Chaz is on the verge of a catastrophic stroke or heart attack.”

As The ENQUIRER revealed, Chaz abused alco­hol and prescription pills – including the powerful painkillers Perco­dan, Vicodin and OxyContin – for a decade before fi­nally getting clean in 2004.

In late 2011, while studying the final stage of the trans­gender procedure, he acknowledged its dangers.

“It’s a big surgery and it’s not totally perfected, and I want to really make sure 100 percent that the pro­cedure I decide to do is the right one for me.”

He is well aware the post-surgical recovery pro­cess usually requires an initial morphine drip and heavy painkillers such as Percocet and Tylenol with codeine – which could reignite his dependence.

Chaz’s long and painful struggle with substance abuse began when he learned Joan Stephens, the love of his life, was dying of cancer. She passed away in 1994, and a heartbroken Chaz confessed: “When she died that ****ed me up for a long time…(I was) a full-blown junkie. I stayed in my house and took pills.”

Chaz bravely attempted to wean himself off painkillers in late 2001 after surgery for the gynecological condition endometriosis – but sadly relapsed when a doctor lowered his dosage of OxyContin.

In his 2011 book “Transition: Be­coming Who I Was Always Meant to Be” Chaz confessed: “I was hooked again…If you keep giving an addict drugs, they will become addicted to them.”

That frightening re­lapse “led to the dark­est period of his life,” revealed the insider.

“Chaz was a social drinker and had de­veloped into a closet drug addict, but in the depths of his substance abuse from 2002 to early 2004, he would remain inside his home and combine the two.”

To make matters even worse, he packed on weight, blaming it on a combination of downer drugs, slow metabolism, poor eating habits and little physical activity.

“Chaz also went on benders – popping pills, drinking alcohol and eating junk food to the point where he’d wake up in his own vomit.

“At times after blacking out on the kitchen floor, surrounded by pizza boxes or left­over pasta, he’d be awakened by pet dogs and cats lick­ing his face.

“And he’d suffer wild hallucinations. He would imagine neighbors bursting into his house ready to torture him because he was a woman wanting to become a man.

“Another time he made a ‘fort’ out of a turned-over living room couch and all the pillows in the house. He then hunkered down with all his pets in anticipation of medical personnel from a rehab facility coming to nab him.

“During one wild bender, a woozy Chaz, clad in pajamas, hit a string of local Los Angeles bakeries and raced home to consume brownies, cupcakes and fruit pies. He then hallucinated about being trapped inside a big cake.

“Even without the food frenzy, the drinking and drugging were a lethal combination,” stressed the insider. “He could easily have died during one of those episodes between 2002 and 2004.”

Dr. Damon Raskin, a Malibu, Calif., addiction specialist, confirmed to The ENQUIRER: “Drinking com­bined with drugs is a deadly combination because it increases the risk of dying from respiratory failure or seizures.”

Chaz has been suicidal in the past, say insiders.

“Right now he IS miserable,” confided a source. “He’s not working steadily, he hasn’t had a real girlfriend since his bustup with longtime partner Jennifer Elia, and he was disap­pointed when he was passed over for the upcoming all-stars season of ‘Dancing with the Stars.’

“He’s also stressed out about the huge decision of whether or not to follow through with the final part of gender reas­signment surgery because of the painkiller relapse risk.

“Just like he’s done in the past, he’s numbing himself with food. He’s ballooned to 345 pounds and has never been heavier.

“He’s back to sitting inside all day – playing video games or watching reality TV and stuffing himself with pizza, tacos and chips.”

Back in March, we revealed Cher was worried sick when Chaz’s weight, which had yo-yo’d for years, rocketed from 270 pounds in 2010 to a whopping 301!

“Chaz is locked in a vicious cycle of self-destruc­tion,” said the insider, “and Cher is trying to help him through the crisis.”