Hopefully it's just a one-off thing, don't worry about it.
However, Eating and spitting is a recognised form of eating disorder, obviously a bit of a mix between anorexia and bulimia. Do you feel nauseous (sp?) at the thought of eating?
If it does become a problem, definately go see your doc, and you might be able to talk to someone going through a similar thing if you look on the eating disorders association forum (edauk.com) I've seen people talking about it in the past.