I feel your pain, Mochi! We're about the same size, and I find that Gap jackets are not reliable for me, either. I'm trying to train my eye to "see" size better -- I can now tell without going into the fitting room if there's enough length in a garment, for instance, and this saves me time while B&M shopping. I am constantly taking in at least two sizes of everything.
You are looking terrific. Your wardrobe has become more focused and more you in the past year, you're looking fit and your recent hair cut has sent your style quotient sky high.
Sometimes I literally speak to the clothes in the dressing room. I mean out loud. In my Diva voice (melodious, but firm). "If you want my money. It's your job to make me look damn good."