FACING a bitter divorce battle with hubby JOHN TRAVOLTA, a stressed-out KELLY PRESTON is at her wit’s end – and friends fear she may do something drastic!

The 50-year-old beauty is terrified she’ll lose custody of the couple’s two children to John in a potential divorce, sources say, and she collapsed after months of arguing over her husband’s gay scandals and their $220 million fortune.

“Things between Kelly and John are getting uglier by the day, and Kelly is cracking under the strain,” confided a source.

“While John is desperate to keep up the facade of a happy family, Kelly can’t take the lies anymore.

“She gamely played along when John dragged her and their little boy Benjamin to Australia in early April. But she totally lost it a few days later during a vacation in Hawaii.

“Kelly was talking to a friend on the phone about her issues with John when she broke the news that a divorce is probably imminent.

“But then Kelly’s friend scared the life out of her by suggesting that if John gets angry enough over her leaving him, he could try to get custody of Benjamin and their daughter Ella Bleu.

“Kelly burst into tears, col­lapsed into a chair and started wailing, ‘I can’t take this! He’ll destroy me if I leave him! My life is over!’ Kelly moaned about not knowing how she’d carry on if her kids were taken away.”

Since marrying the “Saturday Night Fever” star in 1991, Kelly has basically put her career on hold to be a wife and mother to their son Jett – who tragically died at the age of 16 in 2009 – 13-year-old Ella Bleu and Benjamin, 2.

“Kelly’s life has revolved around John and the kids for years,” said the source.

“And she’s faced one embar­rassment after another over John’s alleged gay hook-ups with men. It’s absolutely humili­ating for Kelly.

“But John’s a bully and he’s  made it clear to Kelly that if she files divorce papers, he’ll unleash the full wrath of his high-powered legal team on her.

“Kelly is already suffering from insomnia. She barely sleeps four hours a night, and sometimes she’s so down that she forgets to eat.

“She’s dropped a lot of weight, and some days Kelly can’t even motivate herself to leave the house. It’s a very sad situation.”

As The ENQUIRER has reported, the couple’s 21-year marriage hit rock bottom over the “Pulp Fiction” star’s indifference to Kelly’s sput­tering career and his relationship with Rav Holly, a 42-year-old ob­sessed male fan and photographer with a violent past.

BUT sources say the biggest issue behind the couple’s marriage problems remains a string of lurid gay sex scandals that have exploded around the 59-year-old actor.

Several masseurs have accused Travolta of sexual battery, and two of the men actually filed lawsuits against him. Travolta’s attorney vehemently denied the claims. A website reportedly uncovered documents that it claims reveal Travolta’s insurer paid $84,000 in hush money to the men.

In another shocker, Travolta’s former personal pilot, Doug Gotterba, told The ENQUIRER in a no-holds-barred exclusive in­terview that he was the actor’s gay lover for six years.

The ENQUIRER also interviewed John’s former personal assistant Joan Edwards, who said she worked for him from 1978 to 1994 and told us: “Of course I knew he was gay.”

Adding to Kelly’s woes is the stress of juggling her family drama with work.

“Kelly is stressed to the max,” said another source. “She’s barely holding it together. She put her heart and soul into filming (the sitcom pilot) ‘Keep Calm and Karey On,’ and by the time it was over, she was wrung out.”

A third source added: “Kelly is most upset because she’s stood behind him all these years and looked the other way over his gay trysts. She even showed up on cue when he needed it to seem like they are still a happy family.”

As The ENQUIRER reported John tried to convince Kelly to pass on filming “Keep Calm and Karey On” in Los Angeles because he preferred her to act the part of a stay-at-home mom in their Orlando, Fla.-area mansion.

She headed to Califor­nia anyway, and while ABC passed on the sitcom, “Kelly has been champing at the bit to re-establish herself in Hollywood,” said the source.

“Especially with her mar­riage in tatters, Kelly wants to have her own career and income to fall back on. But John prefers to keep her like a caged bird, and the emotional strain finally caught up with her. After her frightening collapse, she took it easy and rested for a few days.

“But with divorce loom­ing, Kelly realizes the worst is still ahead.”