What is the ruling on one who doubts whether he uttered a divorce or other words, and does divorce occur if he tried to ascertain a previous matter and uttered it while trying to ascertain it?

What you have mentioned does not cause divorce to occur, for divorce does not occur by self-talk. And whoever doubts whether he uttered the divorce or intended divorce by implication, his divorce does not occur, because divorce does not occur with doubt.

Al-Majd Ibn Taymiyyah said: "If one doubts about divorce or its condition, it is built upon the certainty of the marriage."

And whoever utters divorce as a mere linguistic experiment, his divorce does not occur, due to the lack of intention for the word's meaning. Similarly, if a person afflicted with waswasah (obsessive whispering) utters divorce due to the waswasah, his divorce does not occur, and he should disregard these whisperings.