By Karen S. Schneider
May 23, 2005 12:00 PM

Folks on the set of Alias figured Jennifer Garner had just had a few carbs too many. “She likes to eat,” says a source. “Girl has a bagel, gets a pooch and—poof!—everyone thinks she’s pregnant.” This time, it seems, everyone was right. Nine months after Garner, 33, and Ben Affleck, 32, began dating, sources say the couple are three months into a pregnancy. But don’t expect any official statements of joy. In contrast to his very public romance with Jennifer Lopez, the actor has kept his relationship with Garner private. They have spent their together time quietly hanging out in the Brentwood, Calif., neighborhood where they both live: grocery shopping, getting coffee at Starbucks, renting movies at Blockbuster and, oh yes, getting engaged. In early May a close friend spread the news that the two were planning to wed, to the delight of Garner’s parents. “They had their fingers crossed,” a Garner pal told PEOPLE. “They really love Ben.” Soon after, she was sporting a diamond eternity band, although a wedding ceremony would have to be scheduled around work: Garner is already in Vancouver for the two-month shoot of the romantic comedy Catch and Release. Her pregnancy, says a rep for the film, would “absolutely not cause any recasting.” And what about Sydney Bristow, the action hero she plays on Alias? “I’m sure [executive producer] J.J. Abrams is glad he did that episode where Sydney’s eggs were harvested,” says a source. Back in Brentwood, Garner strolled into the baby shop Wonderland on May 2 and later sent an assistant to pick up a $66 stroller blanket in off-white. In Affleck’s hometown of Boston, meanwhile, his mom, Chris, “would like nothing more than to have another grandchild,” says a source. “She will be thrilled.”

Karen S. Schneider. Tom Cunneff, Kwala Mandel, Brenda Rodriguez and Pamela Warrick in Los Angeles, Amy Longsdorf in New York City and Rebecca Paley in Boston