Contrast Piping Sleeveless Midi Sweater Dress

I am 5'7", 125 lbs and a 34ddd chest with 31" waist. I ordered a large and it fit well, I probably could have done the medium. The material is more of a scuba material, not a sweater at all! The fit was fantastic until you got to the chest area, while it does show it a little in the photos the gap that happens between your breast and armpit is just awful. It stands out so far it just looked so bad and there is no way to flatten it down. It also puffs out a bit under the breast area on the sides. The model with the white version kind of shows what I mean. On the right side of her body it's puffed out by the armpit which is how the whole dress looks. If it could have been more like the left side, that is flat and the lines run straight, that would have been great!