I feel you, health anxiety is the worst! Everyone gets sick, everyone vomits from time to time. No cause for alarm. Naturally, WebMD will bring up the worst case scenarios, but these are hardly ever the case. If you were truly sick, your body would be far worse off. Your body is designed to alert you when there is a serious problem, and throwing up on occasion isn't one of them. To ease your mind, go see your doctor and get a physical with blood work. Talk to them about your intense health anxiety and they will probably recommend some sort of medication to help prevent your anxiety. Mine recommended Lexapro and it has made a HUGE difference for me! I had a MAJOR problem with health anxiety, I was self-diagnosing myself with every disease in the book! But, the meds have really helped and I always try and remember something my mother always said to me: You are human, it is natural to feel sick every now and then, to have random aches and pains. Every person does.
You are fine, your health anxiety is telling you otherwise.