Does divorce occur if a man jokingly says to his wife: "Go, you are free and divorced"?

The phrase you uttered is not an explicit divorce, but rather an ambiguous statement (kinayah) by which divorce does not occur without intention. Since there is doubt about the intention, it is not to be considered, and no divorce takes place with this phrase, because the original state is the continuation of the marriage. If there is doubt about divorce or its condition, it is built upon the certainty of the marriage. It appears that the questioner is suffering from obsessive thoughts (waswasah), so she should turn away from these whispers, beware of indulging them and going along with them, and seek help from Allah.