COS Wide-Leg Jumpsuit cotton blue - XS

I remember trying this on at COS in Toronto years ago but I didn't have the money to buy it new. I also remember it fitting quite big so I instantly bought this XS on poshmark. But sadly I do need a bigger size. It's just the most amazing jumpsuit!!!! Tag size XS 100% cotton I would suggest it for a S or M size. I am usually a large. I could technically wear it, but it's just too tight around my chest and the straps are a bit short. *** there is a dark mark (stain?) on one leg, not very noticeable with the flowy fabric. Please see the photos!! ***