Vomiting while crying

My son is 1year 9 months old. Whenever he cries he do vomiting. Then the crying can be for any reason like he wanted to have something and we deny, or he get hurt while playing and start crying, if you shout on him for some wrong action etc.

Previously he only used to vomit when his father used to should on him. But now for every small reason when he cries he do vomit.

He is already very thin. and very choosy about food.

Unable to understand what to do? and how to control? in practice he ate very less and if something happens when he cries he take out that food also out.