After Surgery In 2002, I Have Become Sick And Have

after surgery in 2002, I have become sick and have diarrhea almost every time I eat something. I have been to gastro specialists and have been scoped as well as having colonoscopies. One specialist told me around 2008 that my vagus nerve may have been cut during the 2002 surgery. I accepted that as an answer and put up with the discomfort. I eat very little early in the day because of the symptoms. Yesterday I ate nothing for breakfast and went to work in the yard. I got sick about 1800 hours and went in to eat. I could not eat and had to go to the bathroom. The stool was loose, tarry and black with a brownish tinge. I have gone to the bathroom 4 times since last night with the same results. I have also lost 20 lbs in the last 3 or 4 months. Should I wait to see if this might be a bug of some kind?