One of the world's most famous single women, Jennifer Aniston celebrated her 39th birthday last week... another milestone without a longed-for man in her life.

And the actress, who spent her birthday on the set of her new movie, Travelling, in Vancouver, without even the likes of her pal Courteney Cox around, is said by pals to be growing increasingly lonely.

‘Staying in more'
With all her best friends, including Courteney, Sheryl Crow and her Friends With Money co-star, Joan Cusack, busy with their children and families, Jennifer is, say insiders, "socialising a lot less than she used to."

"Almost every night when she finishes work, Jen goes back to her hotel and eats and drinks by herself," spilled a movie insider. "Just as often, her evenings are a drink and a book. It's pretty much what she does most nights in Los Angeles."

Kids for company?
And the children issue is said to be looming larger for Jen, one year before the big 4-0.

Insisting, "I've never in my life said I don't want to have children. I did and I do and I will," in the wake of her split from Brad, Jen has been plagued by rumours that she wanted to have children with her brief fling, Paul Sculfor, and has been looking into adopting as a way out of her current lonely situation.

Hollywood hermit
"She goes to fewer restaurants than she used to," spilled a pal. "She socialises a lot less than she used to. You never see her shopping." Adding, "She doesn't travel except for those vacations with her friends, the Arquettes."

1990
Charlie Schlatter
Most famous for starring opposite Kylie Minogue in 1989's The Delinquents, Charlie started dating Jen in 1990 after they met on the set of the flop TV spin-off show, Ferris Bueller. "I always say she's a great girl," said Charlie. "Had I known I was making history, I would have been a better boyfriend."

1995
Adam Duritz
During her grungy period, Jen briefly dated the Counting Crows frontman - making the relationship a real beauty and the beast hook-up. And the dreadlocked singer has nothing but praise for the "very nice girl". "There are whole albums credited to Jennifer Aniston, who is a very nice girl I dated for about a week," revealed Adam. "I don't,

1996
Tate Donovan
Jen and the OC actor dated for three years and were even engaged, but eventually their differences drove them apart. "She likes top-notch hotels and luxury, and I like bed and breakfasts," said Tate. "That's the most shallow version."

1998
Paul Rudd
The pair met when Paul starred as Phoebe's boyfriend, Mike, in Friends, and the pair also starred together in 1998 movie, The Object Of My Affection. They have never publicly commented on their brief relationship.

1999
Brad Pitt
Jen and Brad married after a year together, finally divorcing in 2005. Still said to not be fully over the split, Jen said, just after their 2000 wedding, "I will love him for the rest of my life. He's a fantastic man."

2005
Vince Vaughn
As Brad movie on with Angelina, Jen began dating Brad's Mr & Mrs Smith co-star Vince Vaughn, after they starred in The Break-Up together. Now famously reticent about discussing her love life in public, insiders say Vince helped Jen get over her marriage collapse. She called him "loyal."

2007
Paul Sculfor
The Brit model was snapped coming out of Jen's Malibu home, prompting the tabloids to dig up dirt about Paul's past, including his stint in rehab. Pals say the relationship amounted to a "couple of dinners" in June of that year, and nothing more.

2007
Orlando Bloom
Spotted in Mexico together for a mutual friend's wedding, the Brit actor and Jen were linked in October, last year. "When they got down to Mexico, they just gravitated to each other," spilled a wedding source.

Could Aaron be the new man?
Recently, Jen has been linked to her Travelling co-star, Aaron Eckhart, despite rumours pairing her with Entourage star, Kevin Connolly, with a friend revealing, " Kevin kept her in stitches." But on-set sources in Vancouver insist Jen and Aaron have been flirting between takes and expect to see the new couple out and about in Hollywood soon.