What is the ruling on continuous doubt about uttering the phrase "علي الطلاق" (upon me be divorce) during conversations, while being certain that it was not uttered, and does this affect the validity of the marriage?

If a person reaches a severe degree of obsessive doubt (waswasa) about divorce, his divorce does not take effect, even if it was explicit. It is advised to ignore divorce-related obsessions and not to dwell on them as a way to treat them.