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Like clockwork, the Jennifer Aniston belly watch has begun. On the heels of her Hawaiian getaway with suddenly serious beau Justin Theroux, and with wedding whispers ramping up, the stork speculation has switched into high gear.

"Jen's Baby Countdown," trumpets the new issue of Us Weekly.

Seems that after a thorough examination, the mag (via Hollywood Life) has determined that the actress, 42, appeared to have some suspicious midsection swelling at an Aug. 20 anniversary celebration for pals Ellen DeGeneres and Portia de Rossi.

Other supposed signs that the stork may be adding Jen to its delivery route: She was "glowing" and didn't drink any alcohol.

"She looked pregnant," says a spy. "People were noticing and talking about it like it was a fact."

Aniston, who in the post-Brad Pitt era has repeatedly said she wants to be a mom, also apparently hinted that she had been feeling queasy during their extended tropical getaway, leading the mag to posit morning sickness.

"She was very vocal that she had been sick the whole time and even contemplated cutting the trip short," relays the snitch.

The source adds that Jen has gone so far as to nix her longtime nicotine habit: "She's focused on getting her body ready for pregnancy."

Meanwhile, Life & Style ups the ante by declaring, "It's Twins!" The tab, with sources seemingly deep inside Jen's uterus, claims she's been regularly seeing a Beverly Hills ob-gyn since the spring "to see how fertile she is."

"She had blood work done to check her hormone levels," says a source. "It's clear Jennifer wants a baby -- she may even be pregnant with twins by now."

Or she may not.

"We lost count how many times irresponsible tabloids speculate about Jennifer being pregnant," her rep tells Wonderwall. "This is no different from the other times. Complete fabrication."

Jennifer is reportedly taking a yearlong professional breather "to enjoy herself" and has been house hunting in Los Angeles with Theroux, whom she began dating in the spring after he split with his girlfriend of 14 years.

Meanwhile, rumors are a-flying that Jen bought Justin a special gift for his recent 40th birthday: the leather jacket James Dean wore in "Rebel Without a Cause."

The story originated with the British media, which put the bill at around $12,000, which seems about a million bucks shy of the actual price for such an iconic piece of Hollywood memorabilia.

The word from Aniston's camp: The jacket tale is a load of hooey.