No sin is 'major' after seeking forgiveness from Allah, and no sin is 'minor' when done continuously with headlessness of Allah.
The great Muslim jurist al-Qadi ‘Iyad (d. 544) said "The more insignificant you perceive a sin, the greater it will be in the eyes of Allah, and the greater you perceive a sin, the more insignificant it will be in the sight of Allah."
One of the greatest tricks of Shaytan is to make you trivialize your sins, and allow you to feel secure from the punishment of Allah. And Shaytan's greatest deception is to make you lose hope in the Mercy of Allah, even with the minor sins.
No matter what sin you're struggling with, expect Allah to forgive you if you turn to Him, even as you dread the possibility of His punishment. For it is between hope and fear that true iman lives.