I started the jenny craig program a week ago, and i have been having stomach pain, nausea and headaches. can the food cause this?

Probably: Whenever you put food into the stomach, an automatic signal goes to the brain. That is how fullness is indicated from eating. Nausea and headaches are brain effects. Whether jenny craig is responible or not (i doubt that she is) the commonest cause of these symptoms is high calorie malnutrition, particularly all the sweet "junk" that is affecting millions, especially sodas.

Yes: Your symptoms sound like they may be due to an intolerance to soy. Pre-made food products such as jenny craig often contain a fair amount of soy. Try to avoid the products containing soy and see if the symptoms go away.