Pregnancy has Christina Applegate glowing — and, occasionally, flying off the handle!

On Late Night with David Letterman, the expectant star, 38, admitted that pregnancy hormones have  led to some bad behavior.

"I have no filter anymore," Applegate admitted. "Stuff comes out to strangers."

The actress, who costars as Drew Barrymore's older sister in Going the Distance, told David Letterman, "I've always been really kind and…a people pleaser."

Not as much lately. "The other day, my girlfriend took me to the bank," she said, explaining that they "pulled up really close to the ATM. It was really hot. I didn't want to have to walk. I mean, I'm pregnant for crying out loud! I don't need to walk."

When a security guard "yelled" at Applegate and her pal for their illegal parking job, the star lost it. "I was just like, Shhhhh! Shhhhh! It is too hot out to be a douchebag, okay?!"

Applegate quickly stopped herself, though. "What's wrong with me?" she quipped. "I was like, 'Who am I right now?! That's a horrible thing to say to somebody!'"

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A first-time mom, Applegate confirmed her pregnancy last month; the dad is her fiance, musician Martyn Lenoble.

The star hasn't yet revealed the baby's gender or birth date, teasing to Entertainment Tonight in late July that she was "somewhere between zero and 10 months" along.

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