J.S.
Your digestive system is getting ready for labor and delivery. The BRAT diet won't help because you do want to cleanse. Definitely stay hydrated, drinking more water than usual. Remember... if you feel thirsty then you're already dehydrated.
You said you had cramping that then released some diarrhea like stool? Pay attention to that. It could be early stages of labor. Don't eat anything heavy but keep it light and nutritious... and stay away from binding foods.
With my first daughter I was a bit over a month early with her. I had eaten a pasta and shrimp dinner at my mom's house and that evening I could feel that it still wasn't digesting. My prodromal labor, which had already been going on for over six weeks, kicked into active labor. After every bad contraction, I was then on the toilet with digestive problems. It gradually went from regular poop to diarrhea. Had I not been eating normally and been a bit constipated, and not eaten that large meal earlier in the day, I probably would have cleansed much more quickly.