Unfortunately the er won’t do anything bc it is what the flue sounds like to them they will send you home and tell you to take some DayQuil or something. I wouldn’t go back because they probably won’t do anything unfortunately. Have you called your regular doctor? maybe they can help
Keep as hydrated as you can knowing you are throwing up but, ginger ale sometimes helps, ginger tea helps settle upset stomach compazine for nausea, ask pharmacist for suggestions. Call your doctor. Did they do a blood test in ER. Try slow breathing sending warm thoughts your way.