Your bra is not lower set Anna, there just not
were you think they are...
Initially, we have much bigger pects than a women,
most women have very very small pects. When our breast grows,
they sit on top of our pects, and its them that fill most of the bra.
Filling a B cup in 6 month is very unusual, even for a teen, let alone us,
yet we hear of this all the time. The reason, the muscle factor.
I know what I'm talking about, I fit in a 38B in 4 months, yet now 2 years
later, I fit in a 34B, but they are much rounder.
Initially also, when growing the breast tissue tends to be conical, which
is the shape of the glandular tissue beneath, as fats deposit around this,
the breast tends to become rounder. Look at early teens at the beach
and you'll see what I mean.
Most early teees don't wear full cup bras for this reason, they wear triangle
bras, with no support on the top side of the breast.