Why does my cat have a poopy butthole?

So my furbaby, Doobie, has been having an issue lately where sometimes he has poop caught in the fur under his butthole, and when I notice it I have had to manually clean his butt, which me and him both hate and sometimes if I don't take care of it in time he will drag his ass on the carpet and so I now have skidmarks on my carpet.

Has anyone had to deal with an issue like this before? and if so is there anything I can do to make sure he maintains a clean butt? Any advice is greatly appreciated.