Constant yellow stool and gut symptoms?

I have yellow and loose stool on and off for ages now. It is becoming a problem. I can't remember the last time I actually had just a normal stool. I sometimes get burning after the stool, like it is acidic. The colour is usually off, ranging from almost green in colour to light yellow or pale. I often also get bloating and nausea. i am also finding it hard to maintain and put weight on. I also get a pain under my right rib, an ache. The symptoms are worse after eating high fat food. My liver enzymes are slightly raised but my doctor says they are nothing to worry about. I had an abdominal CT scan which said liver and billiary ducts looked normal. I do not have Celiac disease and I don't eat wheat or milk.What is causing these horrible symptoms? i am at a loss. Any help is greatly appreciated.