Is the prayer of a young man who sins by looking at forbidden things and masturbating invalid if he doubts the discharge of semen after performing ghusl?

The negligence you experience in prayer is due to the ill effects of sins, where one sin leads to another, such as masturbation, watching forbidden things, and speaking with non-mahram women. These matters are an entry point for Satan and a great cause of temptation. Allah commanded the wives of the Prophet (peace be upon him), who are the purest of women, to observe hijab, so how about others?

You must get rid of the causes of masturbation, such as intermingling with women and watching forbidden things. Whoever desires to rectify their condition must close the doors of evil and ask Allah for help.

Prayer is not valid without purification. If you are certain that semen has been discharged, ghusl (ritual bath) is obligatory for prayer. Your prayer without purification is invalid. You must repent from the sins you mentioned. As for doubt about the discharge of semen, it does not necessitate ghusl. If you perform ghusl after Janabah (major ritual impurity) and then semen is discharged again, there is a difference of opinion regarding repeating ghusl.

The ruling on one afflicted with seminal incontinence is explained in another fatwa.