It almost sounds like it could have something to do with your gallbladder. I had the same symptoms and I went to the doctor for 2 years before they finally realized I had gallstones. You might want to look into that.
I just happened upon your post from over 2 yrs ago. Did you ever find out what was wrong? I am having the exact same symptoms and I am miserable.
I'm having severe stomach pains after I eat as well as having to run to the bathroom after eating (diarrhea). I just noticed blood and mucus in my stool. I get pains in my chest (stabbing), under my left side of my ribs and around to my lower back, sometimes my stomach feels empty even after I just ate. I'm tired, have headaches & this has all been going on for 1 1/2 months now. Please help!!!