Definitely order a size up. I normally wear a M, and in the pix Im postpartum and couldn't be bothered to put on a proper  bra- so near with me.
 I will say I have a very thin frame, and a large bust,  but the shoulders just  want to slide off, I do have a long torso but the torso is on PattyBoutik  seemed giant in length. I want long shirts but these are always too long. Also the seam down the back was a little weird, and the texture of this material was not four way stretch, but 2 way stretch,  so it felt a little stiff. That said I was pleased that the fabric was thicker than a typical ladies shirt! Thats really nice ! I did return it and Im contemplating trying a size large.