Megan Fox physically bounced back from giving birth in seemingly no time after delivering son Noah in September, but she said her pregnancy was another matter: It was so grueling that she feared she was "birthing a vampire baby."

The 26-year-old “Transformers” star, wife of "90210" actor Brian Austin Green, gave birth to her first son, Noah Shannon Green, on Sep. 27 after a full term. And even by Hollywood standards the actress seemed to be back to her svelte self in record time, later revealing that she had only gained 23 pounds during her pregnancy. Fox debuted her slim figure on Monday night, just two months and a half after giving birth, in a form-fitting blue Roland Mouret dress on an appearance on “The Tonight Show” to promote her new film “This is 40.”

But despite raving about the joys of motherhood – Fox told host Jay Leno, “I love it. It’s my favorite thing that I’ve ever done so far, so I’m happy with it” – she candidly admitted that her pregnancy wasn’t entirely smooth, and neither was the eventual reality of raising a son.

"[The pregnancy] was so bad for me, actually, I thought I was maybe birthing a vampire baby," Fox told Leno, detailing the intense morning sickness she experienced during her first trimester. Fox said that the pain when she began going into labor was so bad that she tried to entreat the security guard at the hospital for an epidural.

Fox also revealed that the difficulties of raising a child were more than she’d anticipated, so much so that she quickly realized she needed additional help. “Having an infant is difficult,” she told the Daily Mirror. “It’s a lot of work and I didn’t hire any help because I overestimated my own abilities.”

“I had no idea how difficult babies could be, so Brian and I were exhausted,” said Fox. "I said to Brian, 'We have to get a night nurse or we're going to get a divorce because someone's got to sleep in this house or we're going to kill each other.’”