Prego powerhouse SNOOKI’s fiancé is two-timing the “Jersey Shore” darling!

The “Jersey Shore” star’s skirt-chasing fiancé Jionni LaValle has been secretly ro­mancing a former girlfriend, say sources.

Blockbuster candid photos, obtained by The ENQUIRER, will break Snooki’s heart because they show Jionni, 24, with hush-hush galpal Erica Wecksler, a 22-year-old brunette fashion merchandiser from New Jersey.

“Poor little Snooki is caught up in a love triangle that she knows nothing about!” a close source told The ENQUIRER.

Jionni openly dated Erica in the past, but then Snooki came into the picture and he ended up impregnating her.

“He’s engaged to Snooki but go­ing behind her back to contact Erica, calling and texting her,” charged the source. “He’s cheating on Snooki.”

Snooki, the flamboyant 24- year-old MTV star, whose real name is Nicole Polizzi, recently confirmed her pregnancy by Jionni, a “Jersey Shore” regular and her beau for the past year and a half. She says they’ll marry after their baby is born in six months.

But their future together is now clouded because Jionni never officially ended his romance with Erica, and as far as she’s con­cerned, she’s still a big part of his life, according to the source.

“Erica says Jionni was carry­ing on a ‘hot and heavy’ affair with her right up until last fall,” confided the source. “She re­cently told a friend, ‘We were seriously hooking up all sum­mer and Jionni considered me to be his girlfriend – not Snooki!’”

For ALL the details and the exclusive photos – pick up the newest ENQUIRER – hitting newsstands today!