It's not your fault that the clothes you buy don't fit your body. They were made to fit someone who is a "perfect 10" (or 4, 6, 8, 12, etc. etc.), which few of us are. And making something as fitted as the Perfect Fit Bombshell Dress is the fastest way to understanding exactly why the clothes you buy don't fit your body. Like today I learned my back is three sizes smaller than the rest of me. I guess that's better than the alternative, but it can throw things off — bra size, for example.
I made it through the first five lessons in Gretchen Hirsch's online sewing course at Craftsy.com. And as you can see, I have a pretty decent muslin made for the bodice now. I had to adjust my pattern to make bigger cups to account for the fact that my boobs start in my armpits. If the tummy looks loose on my dressform here it's because it was made to fit me, not my mannequin (this dressform hasn't had a baby).
Want to see how many pieces go into making something so fitted? Nine pieces for the front bodice: