She was spotted with a sonogram, refused to drink champagne, and just canceled a major world tour. What does it all mean? Sources tell Star the singer is having a baby!

Mariah Carey is singing a different tune about motherhood these days. In the past, she's said she never wanted kids, but hubby Nick Cannon has apparently changed her mind!

Friends tell Star that the couple--who only married on April 30--are overjoyed to be expecting their first child in late spring!

"Mariah tried to keep it a secret, but she's bursting with joy and just can't keep it to herself," one insider tells Star. "She's having a baby and couldn't be happier!"

How did she find out the good news?

"Mariah took a home pregnancy test after she missed her period," says another source. "She was crying tears of joy when she got the result and ran in the other room and told Nick immediately. They weren't really trying to get pregnant. It was more like, if it happens, it happens."

And it did! But Mariah's telling close pals that because she's not that far along into the pregnancy, she's waiting until early 2009 before making any announcements, says the insider. "She wants to make sure that everything is going well and the baby is healthy before letting the world know."

A BOY OR A GIRL?
But Mariah's secret is already slipping out! When Ellen DeGeneres tried to pry the truth out of Mariah on her talk show by offering her a glass of champagne, the mother-to-be smiled and refused it before finally pretending to take a sip. Then, in early December, the 38-year-old was reportedly spotted coming out of an ob-gyn's office in L.A., carrying what looked like a sonogram.

Just days later, she stopped planning an upcoming world tour.

Nick, 28, is especially thrilled at the prospect of becoming a dad, the insider says. "He's completely matured since he and Mariah got married. Nick was surprised when she told him that she was pregnant, but he's been celebrating ever since!"

And Mariah is gearing up to be the perfect mom. "A boy or a girl--it doesn't matter to her," a friend tell Star. adding that the singer is close to sister Alison's children, and she's been very involved with the youth at the Fresh Air Fund's Camp Mariah.

"People think she's a selfish diva, but if you ever saw her with those kids, your impression would change radically," says the pal. "She's going to be an amazing mom!"