How To Test For Lack In Digestive Enzymes?

Hi. I am 57 yes old...female. I live with dissociative PTSD, IBS/C, diverticular disease/moderately severe & I ve been told my pancreas is worn out. I take enzymes with every meal & drink plenty of water. How would the doctor know I lacked digestive enzymes? Do I need to see a Gastroenterologist for accurate testing? I m looking at having the damaged section of the colon removed due to the digestive/constipation problems as well as cyclical bladder infection & diverticulitis approx. every 3/4 myths.