What Causes Recurring Nausea Along With Dry Heaving?

19 year old son has reoccuring nausea with dry heaving. (For over 5 weeks now). Says the nausea feeling is around the adams apple area. Scope is clean, blood work is clean. Ultra sound on Gall Bladder is clean. Chest X-ray is clean, and Upper CT Scan is clean. We are at a loss....please help!.....Carl