You may have something like Chronic Bronchitis or simply be ot of shape.
In either case a little bit of exercise should (in my non medical opinion) help.
It can probably be a very minimal amount of exercise.
Even running for say half a city block, twice a week might help quite a lot.
Also in general (Not necesasarily for this ailment, but who knows? It might help for that, as well) drinking more water is usually good for most people especially those who usually have only soda, and other junk food types of drinks.