Madison's Persistent Cough

Maddy has had a cough and runny nose for almost 2 weeks now and while we've been to a doctor about it, his cough isn't improving. It's weird though because he has a lot of energy and is still his playful self. Also of concern is his loss of appetitie, he doesn't eat very much unless we FORCE him to eat and even then it's not very much. Anyone have any ideas on what else we should try?