If there is vomiting at 22 weeks, you need to have the blood pressure checked, the Rh factor seen and scan to locate twins/ placental abnormalities. If all these are normal you need to see if there is a gastritis/ appendicitis/ a surgical cause for the vomiting. The treatment is to manage dehydration if any, fluid replacement, electrolyte correction and anti-vomit medication with food suitable to prevent vomiting.