Try trying to expand the inhale into the back and sides of your ribs.

Sometimes, just practicing the breath without practicing the movements can be helpful.  Try to inhale for 5 counts, then 6, then 7 ...and so on until your breath capacity improves.  This can be a good exercise while driving, or waiting in line or going to sleep or any other time you simply have a few minutes of spare time.  With a little practice you will improve!  Until then...remember the most important thing is to just breathe!