I'm sorry you're having so much pain.
I don't know why that would be. Hopefully someone on here will be able to offer some helpful suggestions.
I usually get pure liquid in my pouch when all I've had to drink is coffee in the morning. It's normal for the output to fluctuate based on what you've eaten or had to drink. Some foods that help thicken the output are bananas, peanut butter, bread, and potatoes.
I hope your pain goes away soon, so you can enjoy being UC free!