My understanding sister wanted to buy me a new bra for Christmas, but the style I wanted (doubled rear straps, so uncomfortable, but so girly) was not available in my (assumed) A cup size.

So she bought me the B cup size with silicone inserts.

Wow! What a booby revelation. I can fill the B cups without the inserts, they give me full boob support without nipple squashing (the A cups required me to wear nipples shields to stop inversion), and I get so much more support & projection.

The bigger size bra has deeper side panels, a 3 hook deep fastener and wider straps. The support & pushup I get is wonderful. The wide band pushes me forward into the cups, and the straps don't cut or slip.

I really feel like a fully brassiered woman.

Checkout your bra suppliers: the fashion seems to be for broad strapped and deep-banded bras, even for small cup sizes. 

     

good, you are getting the feel of a well fitting bra and you will feel much better now wearing a bra.  A good fitting bra should be felt unless you are doing some arm exercise where you have your arms straight out up/down.