Use Stevia as much as you like and BTW they are finding out that Sugar itself is better than most of the artificial sugars....ugh They just found out that Stevia is good for High BP...Check it out.
I have NO IDEA if This would help but I'd go on a Carrot Juice or even Water FAST for a few weeks to calm everything down. Our Digestive and Eliminative Systems never get a rest and MAYBE yours need a vacation. Probably do nothing in the short haul BUT it Might help.
Another idea is to Just get a Colostomy Bag. It is lousy but at least you'd be OUT Of the Bathroom.
BUT FASTING has LOT'S OF amazing things it can do.....DO SOME Research on fasting and health and stevia.