Kate Upton's Big Boob Blunder: 'They're Growing Out Of Control & Weighing Her Down!'

Curvy Kate Upton is struggling to cope with her changing body during her pregnancy, RadarOnline.com has learned.

"Kate has massive boobs and they're only getting bigger," an insider exclaimed to RadarOnline.com. "They're starting to weigh her down already. She's worried about how enormous they're going to get as her due date approaches."

Upton, 26, is believed to be due in the spring. But she's already sporting a growing baby bump, and having to have clothes specially tailored for her.

"Kate is having custom maternity wear and lingerie made for her, because she doesn't see how anything from stores is going to fit," the source confirmed.

Despite her revealing job, Kate actually dresses pretty plainly in her day-to-day life, and she's working with a stylist to ensure she doesn't look overexposed.

"She's always been happy in her body, but this is one thing that she's having a hard time getting used to," the source added.

At least hubby Justin Verlander, pitcher for baseball's Houston Astros, is enjoying her transformation.

"The good thing is that Justin won't stop telling her how sexy she looks," the insider confessed. "It's a big confidence boost."

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