What Causes Severe Headache Along With Vomiting?

I was diagnosed with a bacterial infection saturday a.m. after fierce vomiting for 6 hrs. after having an IV and a cat scan the dr. said i had an inflamed small intestine. sat. evening i began having diarrhea and headache, both of which have not subsided. i am on 2 different antibiotics. at first i thought i had food poisoning after eating some bad fish possibly on friday night. but my headache is very bad and over the counter meds are not helping much. ?????