I've had food poisoning a couple of times. (Most people have, and just don't know it.) I even got it once while in a hospital!
The most common type, clostridium perfringens, is usually over in 24 hours or so.
Other forms can take longer to recover from.
I'm not a doctor, so I suggest that if you're still having symptoms after a week, you should see a professional.
(Are you sure it's food poisoning, and not something else?)