I can't eat anything without it coming back up. what's wrong ? i feel weak, my head is pounding and it feels as if my stomach is on fire.

Nausea/Vomiting: Nausea and vomiting are common symptoms and have a myriad of causes. Severe stomach pain is an indication to see a physician for a full physical exam and workup.Avoid food until nausea and vomiting have stopped for at least 6 hours. Then, gradually add clear fluids until you can tolerate water then add from there. Read this: https://www.nlm.nih.gov/medlineplus/nauseaandvomiting.html