My 17 week old is taking bromfed (brompheniramine) dm for cough its still not working he is also taking a med for acid reflux has had this cough for over a month?

Many causes: If chest radiograph normal, cough-variant asthma most common cause of cough. 17 week old young but not impossible. Ge reflux, aberrant innominate artery, and subglottic stenosis. Other causes. If reflux occurring several hours after eating , medication for reflux will not work, slow gastric emptying. Sometimes endoscopy necessary to exclude vascular anomaly affecting airway.

Could be many things: Go back to your pediatrician and talk with them about this. This is most likely something simple, but let the doctor help you figure it out.