What Causes Constant Vomiting Post Food Intake In A Child?

Hi i have been havin problems with my son for the past year. He is now two years old. Adam started vomiting his food out when he was around 10 months. Whenever he eats his food he will automatically make himself sick without any effort. It takes me around an hour to feed him each meal and he vomits it within a few seconds. Then i habe to feed him again, then he vomits again, my day goes by like this. Now i just dont have the patience anymore to feed him. We had blood tests done on adam and found that he has lack of iron and vitamin d, can this be linked to the vomiting,? He is two years old now
Ans is still vomiting without putting any effort in or nausea. He could be asleep and just wakes up in the night and vomits all over the bed and then goes back to sleep, or he could just go outside to play and ends up vomiting. It is so stressful that i cannot take it anymore and have become very depressed. I want to be able to look after him without going in to depression

Please help