re: Will adding fiber supplement before bed reduce

There's several different ways to supplement fiber. You sound like you have chronic GI tract irritation. In my experience, this is almost always due to something environmental, dietary, or a combination of the two. So if you don't want to share any of your personal dietary log with anyone that's fine, but then it's all up to you to figure out if it's something you're eating or not. Is it medicine/supplements? Could it be stress related? I don't know, it's a daunting task to figure out what the irritating element is when it comes to your guts.

But, to answer your question, I don't think fiber supplementation would help you, but ......I'd rather say that it's impossible to answer your question not knowing what you're eating. Not trying to pry. "Clean Eating" can be lots of different things. What's your baseline intake of dietary fiber look like?