IT don’t mean a thing if it ain’t got that BLING!

Jennifer Lopez is anxious to get engaged to her young boyfriend of the past two years, Casper Smart, but there’s a catch – she’s insisting he buy her a massive 5-carat rock with his OWN cash! And that’s left poor Casper – a backup dancer whose main source of income is his sugar mama J.Lo – in a tough situation.

“Jennifer is dead-set on marrying Casper, but she feels that he needs to spend his own money on the engagement ring,” a source told The ENQUIRER. “If he dips into his own pocket, it will show everyone how serious he is about her, and how much she means to him.

“Money is a sensitive subject for them because she’s the big breadwinner. But Jennifer points out that he’s earned hundreds of thousands of dollars from her since they got together, plus now he’s getting paid for public appearances and modeling gigs.

“She thinks he can easily afford the type of ring she wants, a flawless diamond that’s at least 5 carats and costs $250,000.”

As The ENQUIRER has reported, the couple have been on the rocks in recent months, with Jen, 44, getting tired of funding the 26-year-old’s spending sprees. Sources say he also feels threatened by former Calvin Klein model Ryan Guzman, 26, who’ll play J.Lo’s teenage boyfriend in her upcoming movie, “The Boy Next Door.”

“Casper is beyond stressed because he really can’t afford a 5-carat diamond ring,” noted another source. “He doesn’t know what to do.”