M.J.
Same problem here but finally at age 42 I am like "whatever". There is nothing I can do about it so I might as well let it go. I am also 5'7 and weigh in the 130s. Before BFing 3 of my kids I was a flat AA. I had gel inserts, wore padded bras etc. Now I am a deflated A. Because of BFing I feel like there is no breast tissue left. I don't even fill out the formed cups of the smallest bra. I have to search out bralets (which thankfully are more comfortable).
What also sucks is that I have a pooch from having 3 kids that I think is more noticeable because I don't have breasts to be more proportionate.
The crazy thing is that I don't care anymore. I am comfortable with my breast size finally. Maybe it's because I am so upset about my tummy pooch. I would get a tummy tuck before a boob job anyday.
Oh and my sister was a nice sized B and after having 2 kids got the boob job to a small C. Her boobs look great but she says it's her biggest regret. Grass is not always greener.