In conditions for extreme headache symptom of nausea
and vomitting is quite common. But the question is why headache? When all your tests are normal the medical parameters indicate towards migraine
or anxiety/ stress
etc. The associated symptom of rashes on your body also gains concern as tagging it with stress may call for review. I think you should also rule out your abdominal worms if any . To get rid of vomits and sickly feeling a little change in life style may work. Morning walk, timely meals, proper meals and amongst herbs you can use fennel chewing after meals, mint pomegranate seeds thyme rock salt may cure your vomits.