Throwing up stomach acid occurs due to either severe, repeated vomiting or vomiting on an empty stomach. The two most common causes are attacks of gastritis, GERD, or gastroenteritis.
Nausea & vomiting.
Abdominal pain and vomiting can be due to several conditions. Acute abdominal pain and nausea are most commonly due to stomach bugs (Commonly due to viral gastroenteritis). Chronic abdominal pain or recurrent abdominal pain and vomiting can be due to several conditions such as chronic gastritis, peptic ulcer disease, GERD, or gallbladder diseases