Wudhu

Experiencing a slight discharge after thinking about something

Q: I would like to know if ghusl is fardh on a woman if she has a thought and feels a slight discharge, but doesn't check it because on every ocassion it is seen to be normal discharge, and not mani.

I always experience this during istinja and have checked on many ocassions, but have recently stopped checking because I experience a lot of normal discharge and know it can't be mani. I am still doubtful. Am I ritually impure for not checking this time?