My first question is that most sources say to contact doctor regarding tests if you have “shortness of breath”, but as a Asthma patient this is not uncommon for me. Also runny nose is common. So how would an Asthma patient discern Covid19 from regular symptoms, only fever?
There are apps to help you distinguish Covid-19 versus other diseases so in your question your mention a runny nose which is a rare or infrequent manifestation of covid-19.
Shortness of breath is a more advanced symptom than cough whereas in asthma shortness of breath is usual.
Furthermore shortness of breath in asthma is due to reversible narrowing of small airways so that should respond to usual bronchodilator medication. But the shortness of breath in Covid-19 is at the alveolar level beyond the small airways and will not be helped by bronchodilator therapy.
In short, if an asthma patient has shortness of breath, fever, and cough where the shortness of breath does not respond to bronchodilator therapy, then in the context of the current covid-19 pandemic there is a high probability that this is covid-19 disease.