Could be gas. One Doc is against all fructose like high fructose corn syrup. I forget why but you could ask your doc or maybe even a health food store.
Low energy point for your lungs is 3:00-5:00 am. Large intestines is 5:00-7:00am. If those organs are not working right, it will be most noticeable at that time of the night.
I suppose abdominal muscles cramping up could cause pain in your back as well,
You might want to se a gastroenterologist. (GI) is a doctor who specializes in diagnosing and treating disorders of the entire gastrointestinal tract.