Am I obligated to do anything because of my excessive thoughts and obsessive doubts about divorce, given that I don't remember if I actually uttered the words of divorce or if that only happened in my mind?

Divorce does not occur merely by excessive thinking about it, or by doubting whether one uttered the phrase "I divorce you" or "divorced." This is because the marital bond originally remains intact and is not dissolved except with certainty, in accordance with the hadith: "He should not leave (his prayer) until he hears a sound or perceives a smell." It is advisable to avoid thinking about divorce and to turn away from such whispers.