It is possible to be a professing Christian and not actually be in the faith. Paul said, "Examine yourselves, seeing whether you are in the faith" (2 Cor. 13:5a). Jesus said, "Not everyone who says to Me, 'Lord, Lord,' shall enter the kingdom of heaven, but he who does the will of My Father who is in heaven" (Matt. 7:21-23).
If you are reading this after the rapture has occurred, it's because you weren't ready. Jesus said in Matthew 25:10 that "those who were ready went in ... And the door was shut."