But at least she's having a little fun with it this time around.
In the new issue of GQ, the actress playfully addresses the tabloids' endless obsession with her womb.
"It's just a weird time, I think," Aniston says regarding the constant pregnancy speculation. "The tabloids, instead of being about alien babies and stuff, it's my triplets, quadruplets...[But] I'm not having triplets. Not having twins. Nor am I having one baby...You heard it here. I'm not knocked up now."
But does Aniston ever think of actually wanting a little rugrat someday?
"I still kind of go with, if it happens, it happens," she says. "I'm calm and peaceful with whatever the plan is. It's not something where I'm going, 'I gotta have a kid!'"
Of course, if and when that day ever arrives, will anyone actually believe her? After all, Aniston has had to spend so much time convincing folks that she's not with child.
"The one time I do say, 'Yes, I'm pregnant!' they'll be like, 'Pfft. Right,' " she jokes.
Then again, maybe that's a good thing.
X17 posted pics of the shindig at the Chateau Marmont in Hollywood that was reportedly attended by about 60 guests including Courteney Cox, Adam Sandler, Emily Blunt, John Krasinski, Jimmy Kimmel and Cameron Diaz.
"Last year, I remember you said something to me about your devotion to the lead singer of Aerosmith, Steven Tyler," Seacrest said. "So, I thought the perfect gift for you would be for Steven Tyler to sing you a version of a birthday song."
Sure enough, Tyler came on the line and proceeded to sing a few bars of his band's hit song "I Don't Want to Miss a Thing," slightly changing up the lyrics.
"I could lie awake just to say, "Happy Birthday,' " he crooned.
"That is not happening," replied a shocked Aniston. "That is the best."