Is it normal for buttholes to get bigger and bigger from anal sex?

Yes. People use my asshole to mix cement and store their winter clothes.

The hole is always the same, its size is pretty standard per human... The only thing that makes it look bigger is the malfunction of the Sphyncter (the tiny circular muscle, that normally maintains constriction of the anus and which relaxes as required by normal physiological functioning)... After several damages and/or systematic abuse (excessively practicing anal sex), it loosens and, eventually, become ineffective... Your thoughts make sence and you got the right point, I just wanted to give you the correct anatomical explaination to your question. :)

I think i will quit getting bumfucked before I start shitting myself.

does it get bigger over time from bowel movements ??? I think I smell a troll.

Because the muscles were torn and damaged internally and won't ever heal. Bad practice to do. Stay away from it.