Passing Green Stools, Fever, Mouth Ulcers. History Of Diabetes, BP, Spondylitis. Causes?

Hi Doctor, My mother 56 years old is passing green motion for almost a month now..she had fever for 4 days and then mouth ulcer last one week.. kidney , liver , tsh , ,sugar,bp seem to be ok..She has diabetis and BP..but they are not high and she is on regular motion..we met a general physician and he gave antibiotic for 5 days..but even after that motion is little green only..She has become very weak and she has spondylitis also..my worry is..is some infection spreading in the body and we are not able to diagnose with normal blood tests or any ulcer kind of thing is there in intestines..how do we find out the root cause..