Can you not use Bellows Breath so fast?

Yes, you can use Not So Fast to counter Bellows Breath.

Not So Fast is a [Reaction] that can counter an enemy spell or ability that chooses a friendly unit or gear. Since Bellows Breath is a spell that chooses (targets) units, it is a legal target for Not So Fast.

When you counter a spell with Not So Fast, the entire spell is countered and sent to the trash, which stops both the initial effect and any repeated effect if the [Repeat] cost was paid.