(CNN) -- Alanna Gerwitz-Stern hadn't worked out a day in her life. She never watched what she ate, either. But after having her first son, Jacob, in December 2009, she couldn't seem to shake the baby weight. Stern had gained more than 100 pounds during the pregnancy, reaching 230 pounds at 5 feet 6 inches tall. She hid under sweatpants, sweaters and athletic gear. "I was embarrassed to even go to the gym," says Stern, 33. "I was so incredibly out of shape, and the people I was working out beside were so incredibly fit. I felt like a real eyesore when I would walk down the street."
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Alanna Gerwitz-Stern gained more than 100 pounds while pregnant
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After struggling for months, Stern found way to lose baby weight in eight months
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Stern got pregnant again with twins after reaching her goal
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Core Concepts' mobile app allows her to stay fit as a working mom
Now a size 4 and down to 120 pounds, @placeholder hopes to inspire other mothers trying to stay healthy through multiple pregnancies.