Coughing toddler

Hi, I know that I can't really get medical advice here that's not what I am aiming for.  But I need some opinions on whether or not I should worry about calling my son's doctor. 
My son has had a cough for almost a week now. It's worse at night and in the mornings and also when he's playing hard. For the most part he can breathe fine but he has gotten so upset coughing that he couldn't breathe for a few seconds until he calmed down. Everything I've  read says that a cough is nothing to worry about unless they are having a hard time breathing. I've brought him into the doctor so many times for a cough that I am afraid they are getting tired of it. What do you think should I call them and see if I can bring him in, or just keep watching him and call them if he gets worse? He is 20 months old