Having lots of trouble with fiber and reliable stool for bottoming, help?

I’m (29M) gay, and I’ve been having some complications with bottoming. A lot of gays recommend fiber supplements to help make things more regular, reliable, and cleaner. All the rave reviews around psyllium husk made me super excited, but it made me unable to poop for 4 days and gave me awful gas. Another friend recommended sunfiber, but that has also made me constipated. I’m not sure what to do or why my body is reacting this way; constipation has never really been one of my main issues.

Should I try benefiber? Should I focus more on diet? Am I doing something wrong? Anything else I should try?