Mandy Moore was warned she only had a “slim chance” of getting pregnant. The 39-year-old actress – who has sons Gus, two, and Ozzie, 15 months, with husband Taylor Goldsmith – recalled how much of a “surprise” it was to be told she was expecting her first child because she’d always expected to have fertility problems. Alongside a photo of herself as a child, she wrote on Instagram: “I’ve always wanted to be a mom. Before bringing my two boys into the world with my love, @taylordawesgoldsmith, I was a mom to many many cats and at times, just as many dogs (and admittedly today, I still am). “But…