"Oh, I was scared to tell my dad, of course!" says the 24-year-old, whose pregnancy was unplanned.
But these days her family is behind her 100 percent. "[My dad] is excited now. I think [my parents] are more excited than we are," Polizzi tells PEOPLE.
"I'm their only child and this is going to be their [first] grandchild."
For now, Polizzi, whose MTV spinoff Snooki & JWOWW premiered Thursday, is at the beach, filming the latest season of Jersey Shore. However, the one-time wild-child is showing a more relaxed, serious side as she focuses on the health of her baby boy and her engagement to student Jionni LaValle.
Why Snooki Settled DownThough Polizzi experienced her fair share of on-screen drama with LaValle while filming in Italy, she says that through their ups and downs, she always knew he was the one.
"When people find the one they love, they feel like their spouse is their best friend and their lover," she explains. "That's how you know you've found your soul-mate, and I've never had that with anyone except Jionni, so I put two and two together and figured he's definitely the one."
She says that having a family with her beau was something she knew would happen, "but it happened a little sooner" than expected.
Still, she's excited to welcome her son this September, and is open to the idea of having another reality show once the baby arrives – if her fiancé gives the okay.
"As long as he's comfortable with everything, I would," she says. "If not, I might have to step back a little. Now we have a child so there are other factors involved."
Whether she's in the spotlight or not, Polizzi says one thing fans can count on is that she and LaValle will have a big family in the coming years – and hopefully, one of those babies will be a girl.
"Girls always want their little mini-me," she says. "I don't know about a mini-Snooki, but definitely a girl."