hi,
My brother has Crohn's disease. He also gets sick if he eats or drink. he become nausea and start vomitting + diarrhea.
google Chron's disease if you want more info.
and if you throw up a lot, remember to drink and eat salty food (I know its hard if you get sick). but dehydration can be very dangerous.
It can be alot of things that make you vomiting blood, but one thing thats sure; its not normal. Contact your doctor and tell him/her about your symptoms(!), and get to the hospital if its really bad (more blood, vomiting, fainting, headache, pain, fatigue,diarrhea).
Good luck to you!
Im not really sure what it could be but I have gotten food poisoned once that caused me to vomit but never did i vomit blood. This sounds like a serious issue, that you should see a specialist before eating or drinking anything. ASAP! Praying that it's not as serious!