Hi. My 15 Year Daughter Has Been Complaining Of Stomach

Hi. My 15 year daughter has been complaining of stomach pains in her upper abdomen (not menstrual cramps) for 3 days. The pain is constant/doesn't subside. She's an athlete, but has not had any injuries. The pain extends to her back and is tender to the touch. Laying down helps. Pain is worse after eating, but fairly constant throughout the day and night. We tried Tums and Pepto Bismol, but neither had any positive effect. Any ideas? Thank you