Chelsea Houska is being told she's "so tiny," despite celebrating the "halfway" point of her pregnancy. The "Teen Mom 2" star, 29, is well into expecting her fourth child – Chelsea is already a mom to 11-year-old daughter Aubree, 3-year-old son Watson, and 2-year-old girl Layne. Chelsea updated her Instagram over the weekend to update fans on her bump progress. The MTV face had gone skintight in a maternity pair of high-waisted leggings, with the blossoming bump shown off. Check it out below.