Breathing problem. It feel like this?

Respected sir/mam Sometimes there is a difficulty in breathing but it is not suffocation and a deep breath is not getting why this is happening? I consulted a cardiologist and took echo and gave ecg and everything is normal, first heart beat was 120 but now it is down to 90. I am breast feeding so no medicine was given but vitamin D tablet was given. It turned weekly×4 then monthly. Is there really a problem like this or is it just me feeling dizzy sometimes why does it feel like this?I have two children and the pregnancy time was fine, the eldest is four years old and 2 nd child is 5 months old.I had this problem about 8 years ago, then Dr. Prescribed calaptin 40 tablet,now Dr prescribed vitamin D tablet