Feeling as if there's a heaviness to your body is a common thing. I think it falls under the category heading of fatigue.
The shortness of breath may be something different, and especially in these days of Pandemic, I suggest that a trip to the doctor is you can manage it would be a good idea. Shortness of breath is a sign of Covid-19.
If you have already been cleared of other medical issues causing the breath shortness, then it may simply be that your body needs to get into better shape. I know, easier said than done. But you can work on it a bit at a time. Taking even a five minute walk and then working up to more may change this for you because your lungs will get stronger. But, of course, be sure to get checked by your doctor and cleared for doing exercise before you start.
Another suggestion: buy a fingertip pulse/oximeter. They are not that expensive, and you can then check your own oxygen levels. It's important these days if you have any kind of breathing issue to do this, because a level of oxygen that is below 90% is dangerous, and if you go much below that you should head for a hospital. Just in case you are not getting enough oxygen, it would be good to check. Long term lack of sufficient oxygen, even if your level is above the danger zone, is very damaging to your health. I ordered the fingertip device for myself because it costs a lot less than a visit to the doctor.
Best of luck.
