This set is stretchy but doesn’t sit the same way it looks on model. Very thin and doesn’t support the girls

This set fit a little weird. I'm 5'7, bra size 32B, waist 27in, hips 40in, & I weigh 145lbs. I ordered a size medium. The pants aren't high-waisted, which is fine but they can barely stay up. The top fits slack, like the sleeves are short but the bra part is baggy. The back of the shirt is loose like it's meant for a wider back. I sewed in the waist and the bottoms fit better, don't know what to do about the top.