I sympathise. Last month, OH and myself awoke with what I assume was norovirus. It started with projectile vomiting then diarrhoea. Mine cleared that day, but OH developed a pink rash all over, a fever of 38.5 despite regular ibuprofen/paracetamol. He was also incontinent of watery diarrhoea on the rug on the sofa and all along the hall as he ran to the toilet 
. He was mortified! I'd thrown the rug in the wash and cleaned the hall (with gloves on and bleach) all before he even got off the toilet seat.
Have you been vomiting, or only diarrhoea? Any fevers? Any blood in the stool? Food poisoning could be from food a few days ago, not just the last meal!
Last year I had a strange episode of just diarrhoea which lasted a week! I felt fine otherwise, no vomiting, no fevers, just diarrhoea after almost ever meal. I avoided most dairy, oily/fatty foods, following the BLAND diet and included kefir and sauerkrat in an attempt to add good bacteria back into my gut.
Generally a sinister cause wouldn't start so suddenly, but the Dr might recommend a scope to check for polyps etc unless a indicative food poisoning cause was found . Depending which country you are in, majority recommend a scope from age 50 onwards anyway. keep us updated with how you get on, and hope you feel better soon x