Hii.. yay vitamin b12 deficency causes vomiting ,as you have said you already took injections ,but still symptoms are persisting then you need to think of other causes too ,for which I need some more details like whats the duration after taking food you throw out because we need to consider aome of esophageal and stomach related causes too . As of now continue taking votamin b 12 injection or re check the levels ,take a ppi with domperidon combination twice a day before eating food,have food in small quantity more frequently avoid binge eating ,less spicy and oily ,regular physical activity,these all above measures should help you . Definitly I wanted to rule out achlasia cardia and any severe reflux disease in you . hope this information helps you thank you