Question:
What if I believed once, but don’t believe any more?

Answer:
If you believed on the Lord Jesus Christ, He saved you forever. The jailor asked Paul and Silas: “Sirs, what must I do to be saved? And they said, ‘Believe on the Lord Jesus Christ, and thou shalt be saved’” (Acts 16:31).

What God doeth…it shall be forever, nothing can be added to it or taken away from it (Ecclesiastes 3:14).