yea exactly what jc said, thats the way i got rid of my even smaller chest... and upsized a little.
also... what does your chest work out look like..
if its made up of like just 5 sets of flat bench, there is your problem.
i try to do 30 sets of chest exercises.
Pec flys or cable pec flys
flat bench
incline dumbell press,
45 degree decline bench press
flat dumbell press
and er... the one where u lay on a bench and bring the dumbell behind your head and pretty much touch the ground and then raise it back up so its above your head.. or Dips