There is not a question of God forgiving you. There is only the question of you asking Him to forgive you. There is no sin to great for Him to forgive. His mercy is as great as His love. Your Almighty Father is just waiting for you to turn your back on your sin and come to Him for reconcilliation. What an awesome God He is!!
I will pray for you to have the courage to talk to your priest. All you need to do is confess and repent of your sin.
I wasted five years of my life, away from the Church, because I was too embarrassed to confess a sin (which I had long before repented). One of my greatest regrets in life is not the sin itself (which was serious), but rather that I didn’t trust God enough to forgive me. That almost lead to my self destruction. Please don’t make the same mistake!