Have you done any regular water enemas? I suggest that first. Because you are so sensitive even a water enema may crash your blood sugar. water enemas and colonics wipe me out these days. coffee enemas too. Although, the really super weak version that I did the first time only wiped me out a little.
You mentioned that you are constipated. What you don't want is for the coffee enema to cause a release and for it to just sit there and then for all the toxins to resurculate. That's what I think happened tomrs when I did it and I felt like crapola. I would start with water for now, get your colon clean and then consider coffee in the future.