short or shallow breath

[Guest guest]

Hi....I´ve been having problems with my ujjayi breath recently. The

fact is that by the time i started to concentrate on my

banddhas,keeping a constant, deep rhythmic breath became an effort

during my practice. I do know that breath is a basic and ought to be

the "engine" moving the practice. But what can i do if i`m feeling

that my breath is kind of shallow ( clavicular breath, somehow) ?

What techniques could improve it?