Hello!
Thank you for the query.
Stool color is caused by bile secretion to the stool and by intestinal bacteria. When one of this factors is impeded, stool changes its color.
Lighter stool,
back pain,
chest pain can be caused by a stone in bile ducts. Such stone obstructs duct and bile is not secreted to the stool. You may also notice dark urine with light stool.
Bacterial infection of intestines can be also the reason of your symptoms. In such case, there is no "good" intestinal bacteria responsible for the stool color.
Back pain should be also checked with
urinary tract infection (sometimes can be caused by diarrhea). Chest pain should be always checked with heart problems.
I suggest you to visit your doctor and have abdominal
ultrasound, blood work, liver tests (AST,ALT,GGTP,AP), amylase, urine amylase, urine analysis,
bilirubin level and stool tests. Heart ECG should be also done.
Hope this will help.
Regards.