Is it possible to repent and be forgiven for a sin committed after violating a covenant with God to refrain from watching pornography, especially given one's weakness in the face of desires and the lack of fulfillment of sexual urges from one's wife?

A Muslim must lower his gaze from forbidden things, abandon love relationships and friendships with foreign women, and repent with sincere repentance. Your wife's inability to satisfy your desires might be a punishment from Allah. Fulfilling covenants is required, especially with Allah, and Allah has condemned those who break their covenants. It is advisable to remember Allah's watchfulness when looking at forbidden things, to keep company with the righteous, to listen to religious tapes, to supplicate for chastity, and to practice polygyny if the Muslim is capable.