How can persistent yellowish discharge connected to menstruation be distinguished from vaginal secretions, and is everything that tends toward a yellowish color considered yellowish discharge, even if it is white with a slight yellowish tinge, and does it necessitate abstaining from fasting and prayer if it is connected to menstruation?

It is clear that the questioner is afflicted with waswasah (whispers from Satan or obsessive thoughts), and she must beware of it and not give in to it. To differentiate between yellowish discharge and vaginal moisture, one can refer to Fatwa no. 121284. If the questioner sees white discharge, then purification has occurred, and merely seeing it with the naked eye is sufficient, without the need to shine a light on it.