I just got my new guinea pig and I think she might be pregnant?

I got her from the pet store about 4 days ago, she was in her own habitat but maybe at some point she was with others. Her nipples near her legs are very long, is that normal? She squeaks when I pick her up but is calm when I put her down. Plus she nibbles on my clothes, is this because she has the pregnant munchies, ha-ha? Every morning I wake up to her bowl flipped over and all the food gone! I feed her 2 times a day, a diet including broccoli straw, tomatoes, celery, carrots, bell peppers, cilantro, strawberries, and her vitamin C pellets. She non stop eats! I can't tell if her belly is big or not, she's a fat guinea pig... Help.