This is Dr. David. I am reviewing your question now and will be with you momentarily.
you need to see a doctor right away and get a chest X-ray or CT scan to check for fluid in the lungs which can make it difficult to breath laying down flat.
new weakness in the heart can back fluid in the lungs which can make it difficult to breath.
low red blood cell counts can make you short of breath.
when was the last time you had blood work or had a chest X-ray?