Cold chills usually indicate some kind of a fever. You may have a minor stomach flu.
I would have said food poisoning, but that usually only lasts for about a day.
If the chills stay, try putting an extra blanket or two at night. If it isn't a fever (in which case you would "sweat it out"), then it will hopefully make you more comfortable.
I know my answer isn't professional (or really that good) by any means, but I hope that my answer could help you.