I just responded to 2 others who have somewhat similar "symptoms" but they don't exist according to their doctors examination, so this unjustified fear that something is going wrong happens to lots of people. Try to stop over-analyzing your breath, and you will likely find that the "deep breathing" problem does not exist. Your body normally makes tens of thousands of breaths all day on its own even if you forget about it.
No one here can diagnose you though, so I only offered suggestions to try to determine if there really is a problem. You should go to the doctor for a proper analysis if you still feel there really is a shortness of breath issue after reading this post and thinking about it,.Write back with your thoughts.