How to convince your parents to let you stay home from school?

i have really bad stomach aches for about a week straight and they arent going away.... i also have a cold... should i stay home from school and if so how can i convince my parents to let me?
i do not have swine flu, they already know about this, the nurse is no help, and a doctors appointment is already scheduled

Answer: 
In my house, if we weren't puking, we weren't sick enough.