Open Question: Please shed some light on my situation.?

My 16 year old daughter has been suffering from constant abdominal pain for a few months now. It never goes away and is draining all of her energy. She is stressed out and it is beginning to stress me out as well. The doctor told her there is no physical illness. He said that it is stress related and if she adjusts her diet and lifestyle it will get better. However, she does not believe this and fears it is chronic and she will have to live with it for the rest of her life. All she has been doing is crying. I want to know if others have suffered from stomach pain for a long time but have overcome it. I want her to belive that stress is really causing this. If you could please share your stories if you have had similar experiences that would really help. I just want to give her some hope so she could resume her normal activites and enjoy life. As a mother I can not see her like this anymore.