Mischa Barton has been through A LOT since she first appeared on "The O.C." over 10 years ago -- and now, she's finally speaking out about her very public mental breakdown.

After a DUI in 2007, Barton found herself under a 5150 psych hold at Cedars-Sinai Medical Center, something she's never really talked about until now.

"We thought, 'Work hard, play hard,'" Barton says of her fast life after the FOX soap hit it big.

"It was a full on breakdown," Mischa, now 27, tells PEOPLE in a new interview. "I was under enormous pressure."

And a lot of that "pressure" had to do with her weight.

"It was always, 'She's too skinny, she must be sick,'" she says. "Then it was, 'She's too big.' I was never the right weight."

With a new movie coming out this Friday and a TV pilot in the works, Barton is on the verge of a comeback..

"I've learned a lot," she says. "I'm stronger now."

We're wishing Mischa the best of luck with her new projects! Check out the gallery above to see how her "O.C." costars have fared since the show went off the air in 2007.

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