Jamie Lynn's Final Stretch

False labor pains and the summer heat have Britney Spears' younger sister anxious to meet her due date at the end of this month

Bigger isn't always better.

Just ask poor Jamie Lynn Spears, who's feeling pretty uncomfortable now that she's nearing the end of her pregnancy.

"She's feeling so large and just feeling all the discomfort that comes with it," a source close to Jamie Lynn tells E! News.

The pregnant teen has also been hit with some mild cramps for the past two days, our insider says.

"Sounds like some false labor pains," says the friend. "But nothing serious enough to go to the hospital over. They called her doctor, but everything's fine."

At least the pregnant teen has plenty of support...

Daddy Casey Aldridge is doing his best to make her feel better, rubbing her back when the cramps kick up, says our source. And her mom is at her side, pitching in with last-minute nursery decorating. But the humid summer heat plaguing Mississippi (where the parents-to-be own a home) isn't helping. Even a brief trip outdoors leaves her sticky with sweat.

"Britney apparently called her recently and ordered her to stay inside, under the air conditioning, as much as possible," the source says. "It was really cute."

Britney and father Jamie have been calling regularly to check in on the mommy-to-be, who is expected to deliver at the end of this month. Unless, of course, the baby's late.

"Jamie Lynn knows first babies have a habit of being late," says the pal. "And she isn't too happy about it. I think she's ready for all this pregnancy stuff to be over and the mommy stuff to start."