Since when is believing you earning your own salvation? Do you have a chapter and verse for that?
Paul said believing is in
contrast to the other things you do to be saved. Believing is not working to earn your own salvation:
"5But to the one who does not work, but believes in Him who justifies the ungodly, his faith is credited as righteousness"-Romans 4:5
See it? To the one who "does not work, but believes". He is
contrasting working with believing, not equating them as you are doing. Believing is not included in the works that can not justify. Believing is exactly the very thing that you are to do to be justified before God.