How do you know if reacurring headache and constant stomachache is caused by stress or illness?

Medical evaluation: A medical evaluation of the headache and stomach ache may identify an organic diagnosis. Stress may occur along with medical illness, so one does not rule out the other. And each can cause the other: physical illness is often stressful, and mental stress can cause or worsen physical illness.

Headaches: Your headaches could be coming from tension, dehydration, lack of sleep/poor sleep, skipping meals, stress, teeth grindgin, sleep apnea/snoring, or chronic sinus problems, or from stress. Best to get checked out.