We went through the same thing with one of our leopard babies.
And since we are curious and both did some studies in biology, we decided to dissect the little girl. And to our amazement, she had eaten 7 crickets of a pretty good size. It caused an impaction in her stomach and she died of this. It could explain the twitching from side to side, geckos tend to push their food down this way. Gasping for air could be because the prey was stuck in the "traché" in french which is the tube that leads to the stomach. It is always important to give the appropriate size of food items and to make sure they don't eat too many at a time. it's better to feed it twice a day a few crickets than a whole bunch at a time. Geckos are piggies...
This could be a possibility as it could be many other things like reaction to chemicals or ulcers in the mouth or repiratory system.