Multi Patterned Fashion to Figure Sweater Dress

Bought this online secondhand thinking it would fit me but it was too big. Don't have enough boob-age to fill out the top properly and there's too much extra fabric in the hips. It's a size 0 (plus size) which I had read was approximately a 12. I think it's closer to a 16 due to the empty space when I wear it and because of the stretch in the fabric. Armpit to Armpit: approx. 19in Hips (widest point): approx. 20 1/2in Length (shoulder to bottom): approx.40in