Hi. From your history you were already suffering from gastroenteritis
. On the top of it you took burger and bear, both of which worsens the problem. That is the reason you had loose motions and undigested food in vomit. I would advise you to take a course of antibiotics , supplementary oral electral (ORS) , probiotic
and refrain from alcoholic drinks and outside food. Headache is due to GI Infection.