I had a burger earlier and now i feel sick. i'm worried about food poisoning. should i take zofran (ondansetron)?

Sure. U can try this: If no improvement or you have diarrhea, fever and or severe abdominal pain, then you will need to be seen to R/o E.coli infection. If your symptoms get better with zofran, (ondansetron) but have recurrent attacks with greasy meals, then you need to have work up done to R/ o gall bladder disease. Will need gall bladder US and or HIDA scan with CCK.