Hi. Thanks for your query. Note the history eating some funky canned tuna and developed headache and pain in abdomen within half an hour. Developed diarrhea, with very bad smell,. This surely is an infection called food poisoning. I would advise you the following: Rush to ER as this can be very dangerous as it is smelling so bad indicates there can be gram negative septicemia which has to be observed keenly. have clinical evaluation and proper treatment. Take probiotics, curds and bananas along with activated charcoal. You may need intravenous antibiotics, fluids and supportive medicines.