Lumi Mozart Open Stitch Sleeveless Cotton Sweater

This is a beautiful high quality knit, however, it pooches out at the side seams near the waist, above the hem. You can actually see this in the photo of the model too. The stripes are a beigey-cream and very dark navy. I debated about keeping it, but I am trying not to acquire any more pieces that I only sort-of like and will probably get rid of after a year or so. I usually wear a small, but occasionally a medium and got this in a medium because small was out. Also I am a little bigger through the shoulders and lats compared to the rest of my proportions, so I thought with this cut a small might be tight across my chest. Perhaps the small would have been more flattering on me, but again it's not available to try.