Nobody is too big of a sinner. The love of God and the sacrifice of Jesus are capable of cleansing the worst of all sin. Even Hitler could have been saved if he would have turned to Christ. You have sinned the same as anyone else. It is just that your sins are yours. They aren't too big for God to wipe away. Sin has no power over God, only over you.
Let me ask you something. Do you think murder and adultery are serious sins? Yes? Well, David, a man in the Bible who was called by God "a man after His own heart," (Acts 13:22), was a murderer and an adulterer. It was not because of David's sin, but because he wanted to dwell in the house of the Lord forever (Psalm 27:4). Anyway, David tried to hide his sin from everyone. But God knew his sins and exposed them. David repented and threw himself on the mercy of the Lord. God forgave him and loved him. God loves you, and he will forgive you if you put your trust in Jesus, and ask him to forgive you of your sins (Rom. 10:9-10).