I have a dry cough after eating a large meal. is this a sign of gerd or acid reflux?

Yes: It certainly could be.

Yes: This could very well be a sign of reflux. But it may be something else also. Check with your doc. Nasolaryngoscopy may become useful - discuss with your doc after complete history and exam.

Possibly: Possibly. Cough associated with large meals could represent 'atypical' reflux symptoms. The more 'typical' symptoms include heartburn and regurgitation. Other possible explanations of the cough could be aspiration or perhaps a hiatal hernia. Both of these would be uncommon in a 22 yo but not unheard of.