How can I stop watching pornography and return to religious commitment and academic excellence, especially as exams are approaching? And is what I am suffering from, in terms of religious and academic decline, a trial or envy?

The academic failure and deviation from rectitude that have afflicted you are due to sins and transgressions. Blame should not be placed on an imagined envier. The way out of this situation is to repent to Allah Almighty for watching those disgraces. Repentance is achieved by ceasing to watch them, resolving never to return to them in the future, and regretting what has passed.