Retching

Retching (also called dry heaving or gagging) is when the motion of the stomach and esophagus goes backward, but there is no vomiting. It can be caused by bad smells, choking or stopping certain medications. It can also be because of stress.
Retching is different from vomiting. During a retch, pressure in the thorax goes down and pressure in the abdomen goes up. In vomiting, both pressures go up.