i measured my self and found out i should wear a b cup but i can still fit in an!

Are you sure? I can still "fit" into an A cup bra but it's not very comfortable, I'm a C cup now. I recommend you to get yourself measured at the store instead of measuring yourself! I measured myself last week and told the woman at the store my size. She told my that it was completely wrong. I've heard countless times that a majority of women wear the wrong bra size. The store clerks are specialized in bra sizes, so go let yourself get measured! :]

Wear whatever size is comfortable, you don't need "support" as such as your breasts are small so just wear what looks and feels good. I find sometimes different makes of bra fit differently despite what it says on the label.

wear your proper bra size.
Get it checked just in case at a bra fitting.
But don't wear your 32 A.
I also fit into a bra that's one size smaller, but it stunts the growth and tightens it.

Wear whichever you are most comfortable with. Bra sizes can be kind of finicky, anyway, so it may not make as much difference as you'd think.

I wouldn't rush it, but the next time you wear a bra, buy a B because if your boobs are growing than they won't be able to fit in an A much longer.