Talk to Gynecologist on Short Breathe

I am 28 years old mother of 3 kids via c-section. My current weight is 61 n height is 4.11. After my 2nd child more than 5 yrs ago i am facing the problem of short breathe even I cant sing a nursery rhyme. I have consulted many general physicians each asked to do so n so test but no one was able to identify the cause or suggest some solution. All my test were clear.