What Causes Shallow And Painful Breathing?

I have CFS - confirmed by Harley Street doctor Need constipation relief to keep bowels working Arms and legs go numb Arms and legs go weak and start shaking Basically all body organs are compromised by poor blood perfusion Recently had what felt like a pressure in the heart - I could breathe without any apparent restriction - but when I breathed in ... even a shallow breath - the pressure of the lungs expanding pressed upon the heart causing extreme pain ... proportionate to the breath. When I laid down on the bed the pain got worse - so I took very shallow breaths until the pain went away. It took about 20 minutes for the pain to start to subside. I am often weak and have very low energy. I have insufficient energy to focus my eyes when my energy is low - but following a syn-actin test I can read the small print of a document without the need for glasses. Any idea why my heart should feel like it has been pumped up - and get pains in my heart when taking the shallowest of breaths. Could one of the heart chambers be failing?