Is my prayer invalidated if prostatic fluid is discharged due to recalling previous pornographic scenes and images, and is it obligatory for me to repeat it because I am unsure of the time it was discharged?

It is not permissible to watch pornographic images or pictures of women because they are among the forbidden things. One must repent from them quickly and not indulge in fantasies. Fleeting thoughts do not entail sin, and mere whispers (waswasa) during prayer do not invalidate it, but they do reduce the reward. If Madhiy (pre-seminal fluid) is certainly discharged due to these thoughts, it nullifies ablution (Wudu') and invalidates the prayer if it occurred during or before it and one did not perform ablution. However, doubt about the discharge of Madhiy should be disregarded.