Welcome to the forum.
, weakness and shortness of breath
can be there due to multiple reasons
1. Anaemia- reduced blood hemoglobin
levels. This can be ruled out by getting a complete blood picture done.
2.Cardiac problem- Missing heart beats are one of the common causes of dizziness or it might happen due to some irregularities in the cardiac impulse. This can be ruled out on having an ECG done.
3.Weakness, any infections in the recent past, lack of proper regular meals, as a side effect of some medicines, etc.
All these factors will have to be ruled out with the help of your physician to come to the actual problem for treatment.
I hope this information has been both informative and helpful for you.