AFTER nearly five years be­hind bars, O.J. SIMPSON’s bizarre be­havior has some of his close friends worried that the former football great has gone gay!

“I don’t know what’s happened to O.J.,” an insider told The ENQUIRER. “He used to be Mr. Macho – a die­hard ladies’ man. He preferred the really fine sexy blondes, but being surrounded by only men has changed him.

“Now O.J. has way too much interest in guys, and he likes to show off his body to the hardened felons when they exercise in the prison yard. He’s doesn’t even talk about women, just about guys.

“It doesn’t sound to me like he’s straight anymore!”

Once a notorious skirt-chas­er, Simpson was convicted in 2008 for robbing memora­bilia dealers at gunpoint the year before. Not long after the conviction, the 65-year-old gridiron great was sent to Lovelock Correctional Center in Nevada to serve a 9- to 33-year prison sen­tence. He isn’t eligible for parole until 2017.

After the recent Super Bowl, the insider says O.J. called him – but he seemed more interested in the way the players looked than what happened in the game!

“He couldn’t stop talking about  Baltimore Ravens receiver Anquan Boldin,” noted the source. He said, ‘Anquan is my man! What a great look­ing guy!’

“Clearly, he wasn’t admiring Boldin just for his football skills. He kept going on about him and some of the other players in a tone that sounded sexual to me.

“That alone wouldn’t make me worry, but O.J. also spends a large part of his time in prison lifting weights. Though his hair is graying, he’s built up his body to where he is really muscular.”

Incredibly, Simpson puts on a one-man show for fellow inmates when they go to exercise.

“He’s like a God to the other in­mates,” said the insider. “He prances around flexing his muscles, wearing only a pair of gym shorts.

“He spends hours in the gym trying to look as good as those guys in the muscle magazines. He works out with several inmates who are really built.”

Perhaps the biggest tip-off that O.J. may now be playing for the other side is his choice of prison companions, according to the source. He says the former la­dies’ man hangs out with a group of open­ly homosexual men known as “The Girls.”

“WHENEVER HE’S LET out into the prison yard, he stays with them,” revealed the insider. “He says, ‘The Girls treat me like I was a king!’

“He claims they flirt with him and even give him massages. Some even call him ‘DJ’ – short for ‘Daddy Juice.’ ”

O.J. has used “The Girls” as his per­sonal posse for years now, added the insider.

“He says he has even gifted a few of the ‘girls’ with candy bars, sodas and toiletries from the prison canteen,” continued the insider. “I’ve asked O.J. why he doesn’t talk about women anymore, but he just laughs it off. He says, ‘Man, what do you think I am? You’ve known me for many years. C’mon, get off all this. There ain’t no women in here! Of course I talk about guys. We’re all guys in here.’

“But I can’t help being concerned about O.J. He certainly isn’t the same man he was before being locked up.”

The insider is not alone in his con­cerns.

A source who’s been close to Simpson for 15 years confided to The ENQUIRER: “It wouldn’t surprise me if he has gone gay.

“O.J. is doing the best he can living in the prison world sur­rounded by men. I don’t know if he has become gay. He always loved women and was a lusty lover, but any­thing can happen to a man behind bars. He has to be the center of attention wherever he is, and in prison he still plays that game. He is the star and has all the other prisoners looking up to him.”

The source added that the only time O.J. previously seemed sexually interested in a man was years ago in a nightclub in Miami’s South Beach, where he swooned for 6-foot-2 profes­sional drag queen Elaine Lancaster.

Even after he was told she was a he, O.J. still wouldn’t give up the chase!

As O.J. gazed longingly at the curvy blonde, one of his companions recalls him saying: “With something that beautiful, who cares?”