Hello and welcome to HealtcareMagic.
The short answer to your question is that it is not
prednisone that is causing your
shortness of breath and left sided pain.
From your description of the course of your illness it is my opinion that your condition of Dressler syndrome, which is
pericarditis, has flared up after you stopped/completed the initial course of prednisone.
The dose of 5mg of prednisone which you re- started is too low to help you with this condition, this is why you have had no relief yet.
You should contact your doctors and get their advise as to what dose of prednisone they may want to treat you with at this time.
Sometimes Dressler syndrome is treated with
aspirin, but I assume that this was already tried with you and did not work, since you were started on prednisone.
I hope you find my answer helpful.
Regards and best of health.