I Am Just Recovering From What I Presume Is Stomach

I am just recovering from what I presume is stomach flu. Symptoms included devastating headache (I don't get headaches, as a rule), dizziness, nausea w/o hypersalivation, vomiting. Could not hold ANY food or liquid down at all, not even one or two ounces of warm water or a bite of toast. Oddly, NO diarrhea, as normally associated with stomach flu (I guess -- am very rarely ill). Symptoms began in morning on 8 Jan and generally subsided in the am of 10 Jan except a milder form of vertigo and balance problems, which persist and get worse when I lie down to rest. I think the reason I got this was a trifecta of stressors including diet and fluids that tended to irritate my stomach lining (more coffee and tea). I couldn't take anything for the headache since I couldn't hold down the water to swallow it with and when I finally could on evening of 9th, that part subsided. My question is this: why does some issue in the stomach cause the vertigo and the migraine-level headache?