Is it necessary to perform ghusl after sexual fantasies followed by a feeling of pleasure, without certainty that semen was discharged, knowing that one suffers from obsessive-compulsive disorder?

The questioner's acts of worship are valid, God willing. She is not required to perform ghusl (definition) (ritual bath) when in doubt about the emission of semen until certainty is achieved. She should disregard obsessive thoughts by ignoring them and convincing herself that they have not occurred, while adhering to dhikr (remembrance of God), reading the Qur'an, and making du'a (supplication). It is also recommended to consult a trusted doctor and the counseling section of the website.