Nice job on the sewing. Good idea for the mock-up first. Some advice:

-try the mock-up on inside out so that your seams are facing outwards, pin any adjustments to the seams and mark this on your pattern, of course this will switch things from left to right, so I always sew mock-ups matching wrong sides instead of right sides

-when sewing princess seams which is what you have on your back, sew a line of stay-stitching on both pieces just inside the seam line and on the piece straight piece, clip into the seam allowance right up to the stay-stitching. This is done to 'stretch' the straight piece to allow the rounded piece to fit in.
You see the 'puckering' on those rounded pieces in your picture? Not enough stretching on the long straight piece.

-you also have one shoulder lower than the other, you can see the back center line swung over to the back left with a pucker up on your shoulder. You'll need to either build up the lower shoulder with shoulder pads to match your higher shoulder (very common solution) or fit the front and back shoulders separately. It's hard to say as you didn't use any shoulder padding in your fitting which you really should do to see exactly how things will fit you.

Otherwise, awesome job working from a drawing and pictures!