Is what is discharged after a wet dream usually semen, and what is the ruling on doubting the discharge of semen after a wet dream when examining the penis?

If one has a wet dream but does not find any wetness, then ghusl is not required, based on the hadith of Umm Salamah, where the Prophet, peace and blessings be upon him, said: "When she sees the water." But if one wakes up and sees semen, yet does not recall a wet dream, ghusl is obligatory, because the apparent reason for its emission was a wet dream that was forgotten. You are not required to inspect inside the penis, as this leads to obsessive doubts, and Allah Almighty says: "And He has not placed upon you in the religion any difficulty." (Al-Hajj/78)