Hi thanks for contacting HCM... Yes you might be right , you can have food poisoning second time as history of eaten outside food is present .. Is there any Mucus , blood present in stool ???? It could be viral , bacterial or parasitic .... Get your stool routine microscopic examination ... If show pus cells and bacteria than antibiotic needed ..like ciprofloxacin .. If showing egg of ameba than metronidazole needed .. If egg of any other nematode parasite like hookworm than albendazole given.... If still needed USG and stool culture will be useful... Also get checked by widal test for typhoid .. Take care Advise : gastroenterologist consultation...