New to anal have a few questions

I am very new to anal sex and have a few questions about being clean. In the past I have used sex toys on myself and it hasn't always been the cleanest. I've never had a shitty disaster but I wouldn't want the guy I'm seeing pulling out and having some remnants.

The two times I have bottomed or tried to bottom I have douched and remnants have come out. Once just little flecks shreds the other time there was a nugget up there I didn't know about. I followed douching with my finger up there couldn't feel any debris and I've called that clean. I've had good results with that.

The guy I've been seeing pretty exclusively bottomed in his previous relationship due to his bf not enjoying bottoming. He has said he also makes a pretty good bottom naturally. He's very regular in the poop department and naturally clean.

He asked if he could fuck me the other night but my stomach had been weird in the days proceeding. There was some fingering and that was all well but I wasn't sure about anal. I wasn't confident in being clean naturally and we were at his so I couldn't douche and such to be sure. I explained the stomach situation and he was like "smart you know yourself."

Is my situation normal?

Do you learn with time/experience how to tell if you would be clean?

Is it a quick check with a finger to check and if all seams well move forward without douching?

I've heard of taking fiber supplements to improve regularity and natural cleanliness. Anything else?

Edit: why the downvote?