Committing adultery is one of the grave sins which is promised evil consequences in this life and the hereafter, but Allah forgives all sins including adultery. He said in the Quran, “Say, O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah. Indeed, Allah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful. “ (Az-Zumar 39:53)

On how should you seek forgiveness from Allah, you have to make a since repentance. First, your repentance should be meant for the pleasure of Allah. It should not be intended for showing off. Second, you must express remorse for the sin you have committed. Third, you must give up this sin. Fourth, you must have a strong resolute not to make this sin again.

Moreover, you must increase of your righteous and good deeds espically praying in congregation at mosques doing other deeds that draw you closer to Allah. You must also close all cracks and avenues that may give room for the shaytan such as mingling with women or talking to them without a legal reason.

Allah Almighty knows best.