Semwn come due to constipation Why this is happening And gusal is required?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

With regard to the reason for this, then you should consult the specialists in the field.

As for the obligation of Ghusl (ritual bath), then if the Mani (semen) comes out during sleep, then Ghusl is obligatory according to the consensus of the scholars.

If it is discharged while you are awake gushing forth with desire, then Ghusl is also obligatory according to the consensus of the scholars.

However, if it is discharged without desire and without force (not gushing forth) but rather due to the said sickness, then there is a difference of opinion in regard to the obligation of performing Ghusl.

The view of the Shaafi'i School of jurisprudence is that it is obligatory, while the view of the majority of the scholars is that it is not obligatory. Perhaps this is the most preponderant opinion. Therefore, it is sufficient for you to perform ablution for the discharge of semen.

For more benefit, please refer to Fataawa 351097, 324949, 82518, and 156063.

Allah knows best.