I did exactly that, I didn't know about a pre cleanse food wise (eating fruits and lightly cooked veggies for a few day.
I don't react to a lot of things, didn't have stomach ache, menstral cramps or gas problems previous to this, so I sailed right through it . First one three days, second one ten days (diabetic fast)2days MCF and than broke it incorrectly. I hope to have a healthier break next time. We learn as we do these. Best to You