Hi there ~
I understand your concerns. I believe that the coughing and ejaculation are not related. I am glad that you have a very health life otherwise and this should not be concerning for you. Cough may be due to very many reasons but you should be focused more on the post-coital cough, I wonder if it is due to vigorous sex. I believe there is no need for concern regarding a potential medical problem. However if the symptoms are definitely related and you are getting worse please consult a qualified sexologist
or an andrologist. I hope this helps.
Take care and have a lovely day!