Remember when you were 17 and a big day on the denial front would typically involve school ("No, I'm not flunking calculus") or socializing ("Of course there was no beer at the party!")? Alas, that's not the case for Jamie Lynn Spears, who has spent the last few days countering rumors of fiancé Casey Aldridge's alleged infidelity and the purported bun baking in her still-warm oven.

"She is not pregnant," her rep assured OK! on Wednesday after the National Enquirer claimed there was a "baby one more time" scenario happening for the mom of almost 4-month-old Maddie Briann.

In a well-timed exclusive this week with OK!, the erstwhile "Zoey 101" starlet insists that she and Aldridge have no plans at the moment to be fruitful and multiply.

"You're way ahead of yourself on that one!" she protests to the mag, which reportedly shelled out a million bucks for her December pregnancy announcement. "We are really happy with where we are right now. There is no rush for anything."

Except maybe to prove their relationship is still on track. The bulk of the interview is spent quashing long-bubbling reports that the 19-year-old Louisiana pipe layer cheated on his teen squeeze with a tabloid-tattling older woman.

"I never had a relationship with her," he says of 28-year-old Kelli Dawson, who asserted to In Touch that they were "hot and heavy" until the spring of 2007. "My only relationship with her was as a friend, and me and Jamie were both friends with her."

When asked directly if he ever had sex with her, he states, "Not the least bit."

Adds Aldridge, "In a small town, everybody knows everybody. But when money's involved, you find out who your friends are."

He also adamantly denies rumors that he knocked up Dawson, declaring, "There was never another girl pregnant, ever. I'm 19. Jamie's the only girl I've ever had pregnant."

(Go on, say it, we'll wait: Oy. Oy. Oy.)

Jamie Lynn introduces Maddie to Wal-Mart on Aug. 6. (©X17Agency.com)

Pipes in Spears, "That is just completely fabricated. He never had an intimate relationship with her, so how would that be possible? Around here, that particular girl is known to make up stories."

As for talk that Casey's eye wandered to a second woman by the name of Whitney, Jamie Lynn again shrugs it off, saying, "What happened was that one of those girls did it, and in this small town when one of them does it, they're all like, 'Good idea.' They all jumped on the bandwagon."

Meanwhile, the teenage parents aren't planning to become teenage newlyweds anytime soon.

"We both agree that we want Maddie to be a little bit older so that she can be a part of it, so that she won't just be sitting there the whole time," explains Jamie Lynn. "We want her to be old enough so that we can enjoy it. We are engaged, and we are really happy with where we are right now. There is no rush for anything. Isn't that right, Casey?"

Not surprisingly, the purse-holding Aldridge agrees, pragmatically observing (with perhaps just the faintest hint of cold tootsies), "Some people think that you should just get married if you have a baby and you're young. I think you should try it out and see."

That seems to be the plan for fellow new parents Nicole Richie and Joel Madden, who are also steering clear of the altar for the time being.

"When we get married, everyone will know. It will happen when it happens," Richie, 27, tells People, which features her on the latest cover with button-cute 9-month-old daughter Harlow, who's now graced the front of the magazine twice in her short life.

"Harlow's a delicate soul," says her not-at-all biased mom, who was recently accused of behaving indelicately to a camera-wielding Swedish tourist. "She studies people. She's very coy. People say that she and I make the same expressions. But everyone says she looks like Joel."

The Good Charlotte front man, 29, has no problem with an offspring who's his spitting image -- at least for now.

"I'm cool with it, as long as she doesn't look like me in a wig when she's 16," he laughs. "I like that she looks like me -- it's my get-out-of-jail-free card."

Bite me! Nicole Richie and a teething Harlow run errands in Los Angeles last month. (©X17Agency.com)

Explains Nicole, "I tell Joel, 'Even when I'm really mad at you, I could never really hate you, because you look like Harlow.' So it's saving you."

According to Madden, he and Richie have already fallen into clearly defined parental roles, specifically, of a doting, veggie-pureeing mom and a fiscally responsible dad.

"She has notebooks and notebooks full of the first time [Harlow] rolled over, the first time she laughed ... Everything she's ever done is in that book. It's pretty cool," he proudly says of his milestone-documenting girlfriend, adding, "She's really good with the baby. I'm really good with finances. All of Harlow's education and all that stuff, I already have planned."

As for any plans to add their brood, Richie balks, exclaiming, "Right now? Oh my God, I need a nap first."