Jennifer Aniston is officially over the hill today.  Yep, she's done, finished, an old hag over all...SIKE.  Sexy Jenny is reportedly going to receive a special birthday serenade from John Mayer, that he wrote just for her!

 "I have to say really, I feel better than I ever felt in my life," Jen told Ellen Degeneres. "I did have a moment, though, over the weekend my first like huh ... I don't want to [turn 40]." Apparently Jen freaked out over finding a gray hair.  "I found a really long gray hair, and it kind of flipped me out...It's not my first, but it's the fact that it was so long. I was like, 'Oh that's been there. How many others are there, and what does that mean? It actually brought me to tears, slightly."

Whaaa? I didn't know that celebrities had insecurities!  Happy birthday Jen!