Gastro or Food Poisoning?

Does anyone know how to tell the difference? I started feeling a touch off towards the end of work, and then have had really bad, high stomach cramps and diarrhoea (sorry tmi) since I got home. No vomiting though. I had toast, an apple, and some carrot/celery with guacamole today so nothing crazy, and don't know anyone with gastro so my paranoid mind goes straight to listeria which can take weeks to show symptoms 😟