Dear friend, welcome to HCM.
was an EKG not done?
pain of costochondritis
would go away with NSAIDs (anti inflammatory pain killers).
an EKG is must to rule out cardiac ischaemia.
the tiny lung nodule does not look significant.
what is the normal range for d-dimer
for your reporting lab?
if it is significantly high as per reference range, you need to rule out pulmonary embolism
by CT pulmonary angio.
was the CT scan
plain or a pulmonary angio?
however, costochondritis would not cause shortness of breath
on exertion generally.
please feel free to seek opinion if you feel things are not improving.
take care and keep me posted .
pl. rate the answer before you close.