Hi, I ve been having stomach pain for the last week, when it first started it was so bad, I went to the ER and done blood work and everything came back fine, it s not as bad as it was but it s still coming and going, the pain also goes into my back, I had my gall bladder taken out 3 years ago so I know it s not that, well today there were dark green patches in my stool, what could be going on?